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Vocabulary ATOM-the smallest unit that maintains the characteristics of an element Nucleus- The center of the atom, contains protons and neutrons Electron Cloud –Region surrounding the nucleus containing the electrons 2

The Atom 4

The Atom 5

Nucleus Protons Neutrons 6

The Nucleus Proton-A positively charged sub-atomic particle (+). Atomic Mass=1 amu The number of protons is the same as the atomic number Li 3 7 The Atomic Symbol The atomic mass The atomic mass 7

Li 3 7 The Nucleus Neutrons –A sub-atomic particle in the nucleus --Has a mass equal to 1 atomic mass unit --Neutron do not have a charge (0) To calculate the number of neutrons in an element… Li 3 7 The atomic number The atomic mass The atomic number The number of neutrons The atomic mass The atomic mass 8

Li 3 7 7 (Atomic Mass) 3 protons(Atomic #) 4 neutrons The atomic number The atomic mass The atomic mass 9

WRITING RESPONSE How many protons does Mg have? How many neutrons does Mg Have?

WRITING RESPONSE How many protons does Mg have?12 How many neutrons does Mg Have? 12

The Atom 13

The Electron Cloud Electrons- Valence Electrons The number of electrons equals the number of protons Sub-atomic particle with a negative charge (-) Electrons behave as if in a 3-D orbit Valence Electrons The outer most electrons Valence electrons are responsible for bonding 14

WRITING RESPONSE How many protons? How many neutrons? How many electrons?

WRITING RESPONSE How many protons? 3 How many neutrons? 4 How many electrons? 3

Bohr Model The first shell can have 2 electrons The second shell can 18

Shells and the Electron Cloud 19

Let’s look at a few elements… Hydrogen 1= Proton 1= electron 20

Let’s look at a few elements… Helium 2=protons 2=neutrons 2=electrons 21

Let’s look at a few elements… Lithium 3=protons 4=neutrons 3=electrons 22

Let’s look at a few elements… 9=protons 10=neutrons 9=electrons Fluorine 23

Let’s look at a few elements… 18=protons 22=neutrons 18=electrons Argon 24

ISOTOPES Atoms that have the same # of protons but have neutrons that have been added, resulting in a different atomic mass.

IONS Charged particles that occur when an atom gains or loses an electron during chemical bonding. If the atom gains an electron- Negative charge Ex: Cl- Most non-metals form negative Ions If the atom loses an electron- Positive Charge Ex: Na+ Most metals form Positive Ions

Losing an Electron = Positive ion Na+ has 11 protons but only 10 electrons Gaining an Electron = Negative ion Cl- has 17 protons but has 18 electrons

What would the charge be on an atom that lost an electron What would the charge be on an atom that lost an electron? Gained two electrons?

Which shows a negative ion? Explain Which shows a neutral atom? Explain Which shows a positive atom? Explain B C