Science Section 1.2
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Science Section 1.2 Science Section 1.2 Presentation Transcript

  • Chapter 1Section 2 
  • Bonding
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. View slide
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. View slide
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. 1.by losing electrons
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. 1.by losing electrons 2.by gaining electrons
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. 1.by losing electrons 2.by gaining electrons 3.by pooling electrons
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. 1.by losing electrons 2.by gaining electrons 3.by pooling electrons 4.by sharing electrons with another element
  • Bonding Atoms form bonds with other atoms using the electrons in their outer energy levels. Atoms have four ways to do form bonds. 1.by losing electrons 2.by gaining electrons 3.by pooling electrons 4.by sharing electrons with another element We will be studying each of these in Section 2.
  • 1 & 2.Gaining and Losing Electrons 
  • Sodium and Chlorine
  • Sodium and ChlorineSodium is a soft, silvery metal.
  • Sodium and ChlorineSodium is a soft, silvery metal. It can react violently when added to water or to chlorine.What makes sodium so reactive?
  • Sodium and ChlorineSodium is a soft, silvery metal. It can react violently when added to water or to chlorine.What makes sodium so reactive? Sodium has only one electron in its outer level. Removing this electron empties this level and leaves the completed level below. Sodium is then stable.
  • Sodium and ChlorineSodium is a soft, silvery metal. It can react violently when added to water or to chlorine.What makes sodium so reactive? Sodium has only one electron in its outer level. Removing this electron empties this level and leaves the completed level below. Sodium is then stable.Chlorine forms bonds in a way that is the opposite of sodium—it gains one electron. When chlorine accepts an electron, its electron configuration becomes stable.
  • Forming Ions
  • Forming Ions As sodium atoms lose an electron they become more stable.
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes.
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes.
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. =
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. = 11 protons 11 electrons (neutral)
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. = 11 protons 11 electrons (neutral) but
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. = 11 protons 11 electrons (neutral) but after losing one electron
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. = 11 protons 11 electrons (neutral) but after losing 11 protons one electron 10 electrons (positively charged)
  • Forming Ions As sodium atoms lose an electron they become more stable. But by losing an electron, the balance of electric charges changes. = 11 protons 11 electrons (neutral) but after losing 11 protons one electron 10 electrons (positively charged) Sodium becomes a positively charged ion because there is now one fewer electron than there are protons in the nucleus.
  • Forming Ions
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron.
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron.
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. =
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. = 17 protons 17 electrons (neutral)
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. = 17 protons 17 electrons (neutral) but
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. = 17 protons 17 electrons (neutral) after gaining but one electron
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. = 17 protons 17 electrons (neutral) after gaining 17 protons but one electron 18 electrons (negatively charged)
  • Forming Ions In contrast, chlorine becomes an ion by gaining an electron. = 17 protons 17 electrons (neutral) after gaining 17 protons but one electron 18 electrons (negatively charged) It becomes negatively charged because there is one more electron than there are protons in the nucleus.
  • Forming Ions
  • Forming Ions An atom that is no longer neutral because it has lost or gained an electron is called an ion.
  • Forming Ions An atom that is no longer neutral because it has lost or gained an electron is called an ion. Sodium ion is represented by the symbol Na+
  • Forming Ions An atom that is no longer neutral because it has lost or gained an electron is called an ion. Sodium ion is represented by the symbol Na+ A chloride ion is represented by the symbol Cl-
  • Bond Formation
  • Bond Formation The positive sodium ion and the negative chloride ion are strongly attracted to each other.
  • Bond Formation The positive sodium ion and the negative chloride ion are strongly attracted to each other. This attraction, which holds the ions close together, is a type of chemical bond called an ionic bond.
  • Bond Formation The positive sodium ion and the negative chloride ion are strongly attracted to each other. This attraction, which holds the ions close together, is a type of chemical bond called an ionic bond.
  • Bond Formation
  • Bond Formation Sodium and chloride ions form an ionic bond.
  • Bond Formation Sodium and chloride ions form an ionic bond. The compound sodium chloride, or table salt, is formed. A compound is a pure substance containing two or more elements that are chemically bonded.
  • Bond Formation Sodium and chloride ions form an ionic bond. The compound sodium chloride, or table salt, is formed. A compound is a pure substance containing two or more elements that are chemically bonded.
  • More Gains and Loses
  • More Gains and Loses Can elements lose or gain more than one electron?
  • More Gains and Loses Can elements lose or gain more than one electron?  Yes!!
  • More Gains and Loses Can elements lose or gain more than one electron?  Yes!! Magnesium, Mg, in Group 2 has two electrons in its outer energy level. Magnesium can lose these two electrons and achieve a completed energy level.
  • More Gains and Loses Can elements lose or gain more than one electron?  Yes!! Magnesium, Mg, in Group 2 has two electrons in its outer energy level. Magnesium can lose these two electrons and achieve a completed energy level. Oxygen, O, in Group 16 has six electrons in its outer energy level. Oxygen can gain two electrons and achieve a completed energy level.
  •  The two electrons, in magnesiums outer energy level, can be gained by two chlorine atoms.
  •  The two electrons, in magnesiums outer energy level, can be gained by two chlorine atoms. The two negatively charged chloride ions are attracted to the positively charged magnesium ion forming ionic bonds.
  •  The two electrons, in magnesiums outer energy level, can be gained by two chlorine atoms. The two negatively charged chloride ions are attracted to the positively charged magnesium ion forming ionic bonds. The compound magnesium chloride (MgCl2) is produced.
  •  The two electrons, in magnesiums outer energy level, can be gained by two chlorine atoms. The two negatively charged chloride ions are attracted to the positively charged magnesium ion forming ionic bonds. The compound magnesium chloride (MgCl2) is produced.
  • 3. PoolingElectrons 
  • Swimming in a Pool of Metal
  • Metallic Bonding - Pooling
  • Metallic Bonding - Pooling We have just looked at how metal atoms form ionic bonds with atoms of nonmetals.
  • Metallic Bonding - Pooling We have just looked at how metal atoms form ionic bonds with atoms of nonmetals. Metals can form bonds with other metal atoms, but in a different way.
  • Metallic Bonding - Pooling We have just looked at how metal atoms form ionic bonds with atoms of nonmetals. Metals can form bonds with other metal atoms, but in a different way. In a metal, the electrons in the outer energy levels of the atoms are not held tightly to individual atoms. Instead, they move freely among all the ions in the metal, forming a shared pool of electrons.
  • Metallic Bonding - Pooling We have just looked at how metal atoms form ionic bonds with atoms of nonmetals. Metals can form bonds with other metal atoms, but in a different way. In a metal, the electrons in the outer energy levels of the atoms are not held tightly to individual atoms. Instead, they move freely among all the ions in the metal, forming a shared pool of electrons.Metallic bonds form when metal atoms share their pooled electrons.
  • Metallic Bonding - Pooling
  • Metallic Bonding - Pooling This bonding affects the properties of metals.
  • Metallic Bonding - Pooling This bonding affects the properties of metals. For example, when a metal is hammered into sheets or drawn into a wire, it does not break. Instead, layers of atoms slide over one another.
  • Metallic Bonding - Pooling This bonding affects the properties of metals. For example, when a metal is hammered into sheets or drawn into a wire, it does not break. Instead, layers of atoms slide over one another.  An ounce of gold can be stretched into a wire 50 miles long.
  • Metallic Bonding - Pooling This bonding affects the properties of metals. For example, when a metal is hammered into sheets or drawn into a wire, it does not break. Instead, layers of atoms slide over one another.  An ounce of gold can be stretched into a wire 50 miles long.
  • Metallic Bonding - Pooling This bonding affects the properties of metals. For example, when a metal is hammered into sheets or drawn into a wire, it does not break. Instead, layers of atoms slide over one another.  A lump of pure gold the size of a matchbox can be flattened into a sheet the size of a tennis  An ounce of gold can be court. stretched into a wire 50 miles long.
  • Metallic Bonding - Pooling
  • Metallic Bonding - Pooling The pooled electrons tend to hold the atoms together.
  • Metallic Bonding - Pooling The pooled electrons tend to hold the atoms together. Metallic bonding also is the reason that metals conduct electricity well.
  • Metallic Bonding - Pooling The pooled electrons tend to hold the atoms together. Metallic bonding also is the reason that metals conduct electricity well. The outer electrons in metal atoms readily move from one atom to the next to transmit current.
  • Metallic Bonding - Pooling The pooled electrons tend to hold the atoms together. Metallic bonding also is the reason that metals conduct electricity well. The outer electrons in metal atoms readily move from one atom to the next to transmit current.
  • 4. SharingElectrons 
  • Covalent Bonds - Sharing
  • Covalent Bonds - Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult.
  • Covalent Bonds - Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. Carbon has six electrons, four of the six electrons are in its outer energy level.
  • Covalent Bonds - Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. Carbon has six electrons, four of the six electrons are in its outer energy level.
  • Covalent Bonds - Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. Carbon has six electrons, four of the six electrons are in its outer energy level. To obtain a more stable structure, carbon would either have to gain or lose four electrons.
  • Covalent Bonds - Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. Carbon has six electrons,  This is difficult four of the six electrons are in because gaining & its outer energy level. losing so many electrons takes To obtain a more stable structure, carbon would either so much energy. have to gain or lose four The alternative is electrons. sharing electrons.
  • The Covalent Bond
  • The Covalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond.
  • The Covalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond. Shared electrons are attracted to the nuclei of both atoms.
  • The Covalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond. Shared electrons are attracted to the nuclei of both atoms. They move back and forth between the outer energy levels of each atom in the covalent bond.
  • The Covalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond. Shared electrons are attracted to the nuclei of both atoms. They move back and forth between the outer energy levels of each atom in the covalent bond. Each atom has a stable outer energy level some of the time.
  • The Covalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond. Shared electrons are attracted to the nuclei of both atoms. They move back and forth between the outer energy levels of each atom in the covalent bond. Each atom has a stable outer energy level some of the time. Covalently bonded compounds are called molecular compounds.
  • The Covalent Bond
  • The Covalent Bond
  • The Covalent Bond The atoms in a covalent bond form a neutral particle.
  • The Covalent Bond The atoms in a covalent bond form a neutral particle. The neutral particle formed when atoms share electrons is called a molecule.
  • The Covalent Bond The atoms in a covalent bond form a neutral particle. The neutral particle formed when atoms share electrons is called a molecule.
  • The Covalent Bond The atoms in a covalent bond form a neutral particle. The neutral particle formed when atoms share electrons is called a molecule. No ions are involved in covalent bonding because no electrons are gained or lost. Ionic compounds, such as sodium chloride (NaCl), are not referred to as molecules, because their basic units are ions, not molecules.
  • Double and Triple Bonds
  • Double and Triple Bonds Sometimes an atom shares more than one electron with another atom.
  • Double and Triple Bonds Sometimes an atom shares more than one electron with another atom. When two pairs of electrons are involved in a covalent bond, the bond is called a double bond.
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds
  • Double and Triple Bonds Here is the sharing of three pairs of electrons between two nitrogen atoms in the nitrogen molecule.
  • Double and Triple Bonds Here is the sharing of three pairs of electrons between two nitrogen atoms in the nitrogen molecule. When three pairs of electrons are shared by two atoms, the bond is called a triple bond.
  • Double and Triple Bonds Here is the sharing of three pairs of electrons between two nitrogen atoms in the nitrogen molecule. When three pairs of electrons are shared by two atoms, the bond is called a triple bond.
  • Ionic vs. Covalent
  • Polar and Nonpolar Molecules
  • Polar and Nonpolar Molecules Do atoms always share their electrons equally?
  • Polar and Nonpolar Molecules Do atoms always share their electrons equally?  The answer is no.
  • Polar and Nonpolar Molecules Do atoms always share their electrons equally?  The answer is no. Some atoms have a greater attraction for electrons than others do.
  • Polar and Nonpolar Molecules Do atoms always share their electrons equally?  The answer is no. Some atoms have a greater attraction for electrons than others do. Why?????
  • Polar and Nonpolar Molecules Do atoms always share their electrons equally?  The answer is no. Some atoms have a greater attraction for electrons than others do. Why????? Some atoms have more protons, therefore more positive pull on the electrons.
  • Polar and Nonpolar Molecules
  • Polar and Nonpolar Molecules Chlorine attracts electrons more strongly than hydrogen does.
  • Polar and Nonpolar Molecules Chlorine attracts electrons more strongly than hydrogen does. When hydrogen and chlorine covalently bond, the shared pair of electrons tends to spend more time near the chlorine atom than the hydrogen atom.
  • Polar and Nonpolar Molecules Chlorine - 17 protons Hydrogen - 1 proton Chlorine attracts electrons more strongly than hydrogen does. When hydrogen and chlorine covalently bond, the shared pair of electrons tends to spend more time near the chlorine atom than the hydrogen atom.
  • Polar and Nonpolar Molecules Chlorine - 17 protons Hydrogen - 1 proton Chlorine attracts electrons more strongly than hydrogen does. When hydrogen and chlorine covalently bond, the shared pair of electrons tends to spend more time near the chlorine atom than the hydrogen atom.
  • Polar and Nonpolar Molecules
  • Polar and Nonpolar Molecules The unequal sharing makes one side of the bond more negative than the other. Such bonds are called polar bonds.
  • Polar and Nonpolar Molecules The unequal sharing makes one side of the bond more negative than the other. Such bonds are called polar bonds. A polar bond is a bond in which electrons are shared unevenly.
  • Polar and Nonpolar Molecules The unequal sharing makes one side of the bond more negative than the other. Such bonds are called polar bonds. A polar bond is a bond in which electrons are shared unevenly.
  • Water The bonds between the oxygen atom and hydrogen atoms in the water molecule are another example of polar bonds.
  • “Get Away, Water!”
  • “Get Away, Water!” When water molecules are exposed to a negative charge, the water molecules line up like magnets with their positive ends facing the negative charge. They are drawn to the negative charge on the balloon. Water molecules also are attracted to each other. This attraction between water molecules accounts for many of the physical properties of water.
  • “Get Away, Water!”
  • “Get Away, Water!” Molecules that do not have these uneven charges are called nonpolar molecules.
  • “Get Away, Water!” Molecules that do not have these uneven charges are called nonpolar molecules. Because each element differs slightly in its ability to attract electrons, the only completely nonpolar bonds are bonds between atoms of the same element.
  • “Get Away, Water!” Molecules that do not have these uneven charges are called nonpolar molecules. Because each element differs slightly in its ability to attract electrons, the only completely nonpolar bonds are bonds between atoms of the same element. One example of a nonpolar bond is the triple bond in the nitrogen molecule.
  • “Get Away, Water!” Molecules that do not have these uneven charges are called nonpolar molecules. Because each element differs slightly in its ability to attract electrons, the only completely nonpolar bonds are bonds between atoms of the same element. One example of a nonpolar bond is the triple bond in the nitrogen molecule.
  • Chemical Shorthand In medieval times, alchemists were the first to explore the world of chemistry. They used symbols to represent elements.
  • Symbols for Atoms Modern chemists also use symbols to represent elements. The symbols are universal. Each element is represented by a one letter-, two letter-, or three-letter symbol. Many symbols are the first letters of the element’s name, such as H for hydrogen and C for carbon. Others are the first letters of the element’s name in another language, such as K for potassium, which stands for kalium, the Latin word for potassium.
  • Symbols for Compounds Compounds can be described using element symbols and numbers. The figure below shows how two hydrogen atoms join together in a covalent bond. The resulting hydrogen molecule is represented by the symbol H2. The subscript 2 means that two atoms of hydrogen are in the molecule.
  • Don’t get confused!2H H2 
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one.
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S Ag2S
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S Ag2S NH3
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S Ag2S NH3 H2SO4
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S Ag2S NH3 H2SO4 NaOH
  • Chemical Formula A chemical formula is a combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. When no subscript is shown, the number of atoms is understood to be one. H2S Ag2S NH3 H H2SO4 NaOH
  • Question 1 What is the term for an atom which has lost or gained an electron and therefore has a net charge?A. compoundB. ionC. moleculeD. polar compound
  • AnswerThe answer is B. When thishappens to an atom, we sayit has become “ionized.”
  • Question 2When two or more elements are chemically bonded to form a substance, that substance is called a _______.
  • AnswerA compound is a pure substance containing two or more elements that are chemically bonded. An example of a compound is salt, or sodium chloride.
  • Question 3A _______ bond occurs when atoms of nonmetals share electrons.A. covalent bondB. ionic bondC. metallic bondD. polar bond
  • AnswerThe answer is A. When this type of bonding happens between metal atoms it is called pooling.