1. Atoms and Ions
SNC2D

2. The Bohr-Rutherford Model
Helium Atom
2 positive protons in nucleus
2 neutral neutrons in nucleus
2 negatively charged electrons in the first energy level

3. Standard Atomic Notation (for a neutral atom)
Atomic symbol
Mass number 80 Br 35
Number of protons
Atomic number (35)
35 p+
Number of electrons (for neutral atom)
35 e-
Number of neutrons
Mass number – Atomic number
(80-35=45)
45 n0
Atomic number

4. Br Neutral Atoms and Ions
When using standard atomic notation you can assume the atom is neutral and the number of electrons is equal to the number of protons
A charge is shown if it is an ion. 80 Br 1–
Ionic charge
(1 extra electron) 35

5. Terms to Know Valence Valence shell Isoelectric with a noble gas
The combining capacity of an element
Valence shell
The outer electron shell of an atom, the electrons in this shell are called valence electrons
Isoelectric with a noble gas
The same number of electrons as a noble gas

6. The Why of Ions
The Noble Gases do not react and do not form ions because they already have what all atoms want: full outer shells.

7. Ions
Many elements want to form stable ions where the number of electrons in the valence shell is the same as a noble gas.
Metals tend to become positively charged cations.
Non-metals tend to become negatively charged anions.
They become ions by gaining or losing electrons (which ever is easier).

8. 1+ Cations Na Na Easier to lose 1 electron than gain 7.
Therefore the atom becomes a cation by losing an electron.
It becomes more stable by losing an electron. It becomes iso-electric with Ne.

9. 1- Anions Cl Cl Easier to gain 1 electron than lose 7.
Therefore the atom becomes an anion by gaining an electron.
It becomes more stable by gaining an electron. It becomes iso-electric with Ar.

10. the first syllable + the suffix “ide”
Anions
The elements that form negatively-charged ions are non-metals.
Non-metals, when they form ions, change their names to:
the first syllable + the suffix “ide”

11. Anion names chlorine fluorine bromine oxygen sulphur nitrogen
phosphorus

12. Valence Practice
Given the following Bohr diagram, what will the valence of the ion be?

13. Try These…. Name the following ions: [K]
Mg b) O2- c) Br- d) N3-
Suppose that a new element has been made. Chemical tests show that it is an alkaline earth metal. [I]
Predict how many electrons will be in the outer orbit.
Predict the ionic charge of the ion that this element forms.
Justify why these ions do not exist under normal conditions. [A]
K2+ b) O-

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