Download Chemistry study guide 09

Atom
Atoms are made up f 3 smaller particles:

Protons: Found in the nucleus

Neutrons: Found in the nucleus
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Electrons: found outside the nucleus

Protons & neutrons both have a mass = 1 atomic mass
Electrons have a mass of 1/2000 very tiny
Atomic number is the number of protons in an atom
 atomic number/ number of protons
 atomic mass
Atomic mass: this is the mass of the particles found in the nucleus/ always a decimal
Mass number: the atomic mass round to the nearest whole number
Neon mass number is: 20
Ex: Neon
Protons: 10 (look at atomic number to find)
Electrons: 10 (same number of protons)
Neutrons: 10 ( Mass # = #of protons + # Neutrons)
20 = 10 +10
Isotopes:
1. Atoms of the same element with a different number of neutrons
2. This different number f neutrons gives those atoms different Atomic masses
3. the Atomic mass of an element is based on the averages of its Isotopes.
Ex:
Energy levels: Theses are the levels where the electrons are found around the nucleus of
the atoms.
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Higher the levels # the more energy
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Each level holds a certain number

Maximum # is only achieved in the 1st 4 levels

Outer level or last level is the one that is involved in bonding atoms
together to form compounds
Compound- 2 or more elements/ forms a new substance
EX: Hydrogen + oxygen= combines to form water
EX: H2SO4
2 hydrogen atoms
1 sulfur atom
4 oxygen atoms
2NaCl
2 sodium atoms
2chlorine atoms (coefficient like 2 means multiply
everything by 2)
Valance electrons: the # of elements found in the outer or last level

Bounding of atoms

Maximum # of electrons found in these level are 8 except in the 1st level it is 2
Lewis Electron Dot Diagram:

Electrons are found outside the nucleus

Spin around the nucleus in different energy levels

The electrons in the outer most level- take part in making compounds (Valence
electrons)
Determine Valence:
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There are 8 columns/ maximum # of valance e- is 18

Ex: Neon valance is 8/ it’s in the 8th column
Radioactivity:
1. Nuclear Fission-split the nucleus into 2 smaller nuclei or roughly equal mass
2. Nuclear Fusion: joining together 2 nuclei of smaller masses into 1 large-mass
nucleus

Need temp. over 1 million Celsius

Stars/sun
3. nuclear Transmutation: when one element changes into another element

Ex: U-238
Atomic #
92
Alpha decay:
Nucleus release 2 protons +
Helium nucleus 2 neutrons o
4 Amu
charge is +
Th-234
atomic #
90
2. Beta decay-release an e-from nucleus
atomic # increases by 1
mass = doesn’t change
3.Gamma decay- a release of huge quantities of energy by the nucleus
need to look at examples in notes