Do NOT make an ATOM an ION unless it tells you too! THIS MEANS- Do NOT make an ATOM stable unless it tells you to do so . To determine the charge of a picture of an atom look at the number of protons and electrons in the picture and determine the charge. (Examples are on the next slide.)
Review: What is the charge of this ATOM ? Just use the number of protons and electrons that are given .
What is the charge of this ATOM? Just use the number of protons and electrons that are given. -2
We will discuss: Chemical Symbol Atoms Elements Bonds Compounds Molecules Chemical Formulas Endothermic Reactions Exothermic Reactions
All matter is made of _____________.
Why would an atom combine with other atoms? To make the atom stable When an atom combines with another atom, this forms a ______________________? Molecule
When atoms are joined together, they form a
Atoms bond together for a very simple reason: atoms like to have full valence shells . (8 electrons)
Atoms will share, give away, or gain electrons when forming a bond.
Substances in which 2 or more elements have bonded together form a material with unique chemical properties.
Example : water - 2 Hydrogen atoms bonded to 1 Oxygen atom. H2O
6 C 12 Chemical Symbol
Are made of ______________ that have been joined together.
Molecules form when atoms join Element Compound There are two types of molecules
If a substance has two or more of the same atoms it is a molecule that is an Element
Ex. O (the oxygen we breathe) is made out of two oxygen atoms
Other examples of Element Molecules:
2 2 3 3
Molecules Element H 2 If all atoms in a molecule are alike, then the molecule is classified as an _______________. ELEMENT
Molecules form when atoms join Compound The other type of molecule is a compound. Do you think that the atoms joined together in a compound are all the same? NO! The atoms are different.
A combination of two or more different elements (atoms)
1 Na atom + 1 Cl atom = the compound NaCl
2 H atoms + 1 O atom = the compound H O
The examples above are compounds because the molecule is made out of _____________ atoms.
Energy in Chemical Reactions
Often energy is released or absorbed in chemical reactions.
Where does the energy come from?? Bonds break or form from electrons being lost or gained.
Energy is released when there is less energy in the products than the reactants. This is called an EXOTHERMIC reaction.
If energy is absorbed there is less energy in the reactants than the products. This is called an ENDOTHERMIC reaction.
Exo = out Endo= in
Chemical Formulas- represent a molecule O C O The chemical formula of this model is CO 2
2 C Chemical Symbol
The Chemical Formula use symbols and numbers called subscripts to show the elements and number of atoms that make up the molecule.
2 Chemical Symbols Subscript Note: there are 2 hydrogen atoms and 1 oxygen atom. The one behind the O is imaginary. How many atoms are there? _____ 3
There are ______ atoms of hydrogen and _____ atoms of oxygen.
The name of the elements which are ____________ and ______________.
2 2 1 Hydrogen Oxygen
CO represents? Co represents? Fe O represents? 2 3 1 atom of carbon and 1 atom of oxygen 1 atom of cobalt 2 iron atoms and 3 oxygen atoms
Chemical Formulas cont.
Writing chemical formulas:
Follow right to left pattern on the Periodic Table of Elements
Ex. NaCl sodium is a metal located on the far left and Cl is located farther to the right
Therefore, the formula is written as NaCl instead of ClNa
If a molecule is made out of one type of atom, it is called
If a molecule is made out of different types of atoms it is?
Chemical equation tells about a chemical reaction.