Periodic Table

Identify the position of an element in the periodic table by its electron configuration

Periodic table is divided into several blocks

-To identify the block of an element, look for the highest energy electron—orbital s,p,d,f???

-To identify period of an element, look for the highest numbered main shell – 1,2,3,4….????

-To identify group of an element, look for the total number of electrons in the outermost shell –1,2,3,4,5..?

Electron configuration Block Period Group

1s2 2s2 2p6 3s2 3p6 3d10 4s2 1s2 2s2 2p6 3s2 3p6 3d54s2 1s2 2s2 2p6 3s2 3p6 4s2

1s2 2s2 2p6 3s2 3p4

1s2 2s2 2p6 3s2 3p6 3d14s2

1s2 2s2 2p3

EXAMPLE

Trend across periodic table

-Atomic radius decreases across a periodic table from left to right. WHY?= Nuclear charge increases when across a period from left to right, as the number of proton in the nucleus increases.= Although the number of electrons also increases, the outer electrons are all in the same shell.= Electrons are attracted more strongly to the nucleus.

Atomic Radius

Ionisation Energy = The minimum amount of energy needed to remove one mole of electrons from one mole of atoms in its gaseous state

X (g) X+ (g) + e ∆H=First ionisation energy

First ionisation energy increases arcoss a period from left to right. WHY?= As atomic radius decreases across a period. = the strength of attraction between the outer electrons and the nucleus increases.=The energy required to remove the outermost electron from an atom increases.

Ionisation Energy

Electronegativity = The ability of an atom to attract electrons toward itself.

When across a period from left to right, electronegativity increases. WHY?= Due to the stronger attraction that the atoms obtain as the nuclear charge increases

Electronegativity

Metallic and non-metallic character

Example of metalloids = germanium, silicon, arsenic and tellurium

When going down a Group…

Metal-Down the Group

- Electronegativity decrease (No. of shell increase, Distance between nucleus and outer shell electrons increase)

- More able to donate electrons to form cations

Non- metal- Down the Group- Electronegativity decrease, because the no of shell and distance between nucleus and outer electrons increase

- Non-metals become less able to accept electrons to form anions

The element of group 18-The Noble Gases

-Very unreactive gases- have very low melting and boiling temperature-The lack of reactivity arises from the arrangement of electrons in their atoms – duplet & Octet