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- Introduction to Atomic Structure
- ATOMS <ul><li>Considered the building blocks of matter </li></ul><ul><li>Made up of three main subatomic particles: </li></ul><ul><ul><li>Protons </li></ul></ul><ul><ul><li>Neutrons </li></ul></ul><ul><ul><li>Electrons </li></ul></ul><ul><li>All protons are identical, regardless of the element in which they are found. This is also true for neutrons and electrons. </li></ul>
- Nucleus <ul><li>Atoms have a small, dense nucleus in the middle but most of the atom is nothing more than empty space! </li></ul><ul><li>Extremely small in size relative to the atom but it contains 99.99% of the atom’s mass. </li></ul><ul><ul><li>If the atom were enlarged to the size of a football stadium, the nucleus would be the size of a bee! </li></ul></ul><ul><li>Contains 2 of the 3 subatomic particles </li></ul><ul><ul><li>Protons (+ charged particles) </li></ul></ul><ul><ul><li>Neutrons (neutrally charged particles) </li></ul></ul>
- Atomic Mass Units <ul><li>Mass of proton = 1 amu (atomic mass unit) </li></ul><ul><li>6 23 amu = 1 gram </li></ul><ul><li>Neutrons have slightly more mass than protons but they are considered equal. </li></ul><ul><li>Mass of neutron still = 1 a.m.u. </li></ul><ul><li>Mass of electron is tiny even on an atomic scale (0.0006 amu). </li></ul>
- Atomic # <ul><li># of protons in nucleus determines the atomic number of an element. </li></ul><ul><li>This identifies the element! </li></ul><ul><li>Hydrogen--Atomic #1 = 1 proton </li></ul><ul><li>Helium--Atomic #2 = 2 protons </li></ul><ul><li>Oxygen--Atomic # 8 = 8 protons </li></ul><ul><ul><li>All atoms with 8 protons MUST be oxygen! </li></ul></ul><ul><ul><li>The # of protons in an atom CANNOT be changed (otherwise, you will have a different element!) </li></ul></ul>
- Isotopes <ul><li>Even though the # of protons will never change, the # of neutrons can vary from atom to atom. </li></ul><ul><li>Atoms of the same element that have the same # of protons, but different number of neutrons are called isotopes . </li></ul><ul><li>Every single atom is going to be an isotope of that element! </li></ul>
- Isotopes <ul><li>Hydrogren has 3 different isotopes (all of them have 1 proton) </li></ul><ul><ul><li>Protium (no neutrons) </li></ul></ul><ul><ul><li>Deuterium (1 neutron) </li></ul></ul><ul><ul><li>Tritiuim (2 neutrons) </li></ul></ul><ul><li>Every atom of “H” is going to be one of these isotopes! </li></ul>
- Mass number <ul><li>Mass # of an atom is the sum of the protons and neutrons in its nucleus. </li></ul><ul><li>The electrons are ignored because they are so small! </li></ul><ul><li>The mass number varies for different isotopes of an element. </li></ul>
- Mass number <ul><li>Carbon has two known isotopes: </li></ul><ul><ul><li>Carbon-12 (6 protons and 6 neutrons) (6 electrons) </li></ul></ul><ul><ul><li>Carbon-14 (6 protons and 8 neutrons) (6 electrons) </li></ul></ul>
- Atomic Mass <ul><li>Any sample of an element as it occurs in nature contains a mixture of isotopes. </li></ul><ul><li>The atomic mass of an element is the average mass of all the isotopes of that element. Therefore, the atomic mass is usually not a whole number. </li></ul>
- Atomic Mass <ul><li>For example, the atomic mass for carbon is 12.011 </li></ul><ul><li>Remember, there are two naturally-occurring isotopes: C-12 and C-14 </li></ul><ul><li>Since the atomic mass is much closer to “12”, this tells you that there are MANY more atoms of Carbon-12 than there are Carbon-14. </li></ul>
- Electrons <ul><li>Electrons have a negative charge and are found outside of the nucleus. </li></ul><ul><li>In an uncharged atom, the # of electrons = # of protons </li></ul><ul><li>Always assume that the atom has a zero charge and is neutral. </li></ul>
- Ions <ul><li>Sometimes, atoms will either lose or gain electrons. </li></ul><ul><li>When this happens, they do not equal the # of protons, and the atom becomes positively or negatively “charged”. </li></ul><ul><li>These charged atoms are called ions . </li></ul>
- Electron Cloud <ul><li>Space in which electrons are found. </li></ul><ul><li>Arranged in energy levels: </li></ul><ul><li>Lower energy level = closer to the nucleus </li></ul><ul><li>Higher energy level = further from nucleus </li></ul><ul><ul><li>1 st energy level - 2 electrons. </li></ul></ul><ul><ul><li>2 nd energy level -8 electrons </li></ul></ul><ul><ul><li>3 rd energy level -18 electrons </li></ul></ul>
- Electron Cloud <ul><li>An atom’s bonding ability is determined by the arrangement of electrons in the outermost energy level. </li></ul><ul><li>These are called valence electrons. </li></ul><ul><li>Atoms that have only one electron or those that only need one electron are much more likely to bond. </li></ul><ul><li>Some elements have a complete set of electrons and will not bond (Noble Gases) </li></ul>
- Quarks <ul><li>It is possible to get even smaller than these three subatomic particles. </li></ul><ul><li>Current theory states that protons and neutrons are themselves made up of even smaller particles known as quarks. </li></ul><ul><li>There better our technology gets, the more subatomic particles there are being discovered. </li></ul>

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