Atomic Structure and Periodic Trends

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3Li – Lithium – remember: can’t have s3 (Pauli)

Configuration 1s22s1

Easily ionised to Li+ (1s2)

Alkali Metal

Under standard conditions: lightest metal and least dense element

4Be- Beryllium

Configuration 1s22s2

Be2+ (1s2) stable ion

Alkaline Earth Metal

Toxic: replaces Magnesium from Magnesium activated enzymes due to stronger coordination ability

Slide 91

5B - Boron

Config 1s22s2 2p1

Forms stable covalently bonded molecular networks

Mainly tervalent

Lewis acidity of many of its compounds and multicentre bonding

Chemistry highly diverse and complex

Number of Electrons: 5

Slide 92

6C - Carbon

Config: 1s22s2 2p2

Diamond, graphite, amorphous, fullerenes (e.g., C60)

Forms (usually) four bonds (tetravalent), see CH4

Non-metallic

Carbon's unique characteristic of bonding to itself is responsible for complex molecules composed of long chains of carbon atoms, the skeleton of life

Slide 93

7N - Nitrogen

Config 1s22s2 2p3

In compounds typically forms three bonds (trivalent), see NH3, N2

Non-metal

N2:

Gaseous, odourless, tasteless

78% of air is N2

Very inert at room temperature (and below) due to strong triple bond

Slide 94

8O

Config 1s22s2 2p4

member of chalcogen group

Normally considered divalent but other oxidations states vary widely

hugely electronegative (see later)

Colourless, odourless, highly reactive gas,

Created biologically from CO2 by green photosynthesizing plants

Paramagnetic (attracted by a magnetic field)

O2:

Slide 95

Exercise 3;

Name the electron configurations of the F and Ne atoms. Which is more stable and why?

Slide 96

9F

Config

Member of the halogen group

Most reactive of all elements

Forms F- readily

highly electronegative!

Does not exist in nature in the elemental state at all because of high reactivity

Slide 97

10Ne - Neon

Config

Full Outer shell

Noble Gas

Unlikely to form bonds or ions

Slide 98

And now the cycle repeats itself….

Remember:

Li: 1s22s1

Na: 1s22s2 2p63s1

Ne: 1s22s2 2p6

1

2

3

4

5

6

7

s1

s2

p1

p2

p3

p4