Bohr Models and Valence Electrons

Bohr Models + Ion Formation

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What we will learn

• current atomic model recap

• electron shells/configuration

• drawing bohr models

• ions and ion formation

Atomic Structure

• Protons + neutrons = nucleus

• Electrons = in orbital shells

• These are the shells we will be learning about, and the distribution of the electrons in them

Electron Shells

• Shells around the nucleus can hold certain amounts of electrons (energy)

• 1st shell = 2 e

• 2nd shell = 8 e

• 3rd shell = 8 e

  • can hold up to 18, ​but for our purposes we will cap it at 8

• Most outer shell = the valence shell --> where it can gain or lose electrons

• Valence shell needs to be full for an atom to be considered stable

Drawing a Bohr Diagram

1. Determine numbers of subatomic particles

2. Draw the nucleus

3. Draw the 1st shell

4. Draw subsequent shells (like a clock) until all electrons are shown

Multiple Choice

What is the atomic number of this element?

• 17

• 18

• 35

• 35.453

Multiple Choice

What is the mass number of this atom?

• 1
• 3
• 4
• 7

Multiple Choice

How many electrons can fit on the 1st energy level (orbital) for any Bohr Model?

• 2

• 6

• 8

• 10

Multiple Choice

What element is represented in this Bohr Model?

• Carbon

• Hydrogen

• Aluminum

• Lithium

Ion Formation

• an ion is a charged particle Or an atom that has gained or lost electrons

• positive ions = cations = LOST an electron

• negative ions = anions = GAINED an electron

• this loss or gain happens to stabilise an atom (give it a full outer shell)

Naming Ions

• Positive ions (cations) keep the name of the atom they are made from. E.g. copper becomes copper ion

• Negative ions (anions) use part of the atom's name and add -ide onto the end. E.g. fluorine becomes fluoride ion

• We write out their chemical symbols with a little superscript + or - and the number of electrons they lost or gained.

Multiple Choice

Where are valence electrons located in an atom?

• On the outermost energy level

• On the innermost energy level

• In the nucleus

Multiple Choice

Atoms from group 2 on the Periodic Table are likely to form ions of what charge?

• +1

• +2

• 0

• −1

• −2

Multiple Choice

How many electrons are in a Li⁺ ion?

• 1
• 2
• 3
• 4

Multiple Choice

What is the charge of an atom that has gained one electron?

• -1
• -2
• +1
• +2

Multiple Choice

Fluorine, like all halogens, has 7 valence electrons but wants a full shell. What charge will fluorine make?

• 7+

• 7-

• 1-

• 1+

Extra: forming bonds

• to lose or gain electrons, they need to go somewhere

• they often go to other atoms who need to lose or gain an electron

• this is called chemical bonding, the sharing or exchange of electrons

• atoms will balance each other out to form stable valence electron shells

Multiple Choice

How many electrons are in a Li⁺ ion?

• 1
• 2
• 3
• 4

Multiple Choice

What charge will a Beryllium ion have?

• +
• 2+
• 2-
• -