Chemistry (mr mcdermott)

Ionisation energy, shells, trends of the periodic table and bonding

Define first ionisation energy

Define first ionisation energy

The energy required when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge

Show first ionisation energy with hydrogen

H(g) --> H+ + e-

Define second ionisation energy

The energy required when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge

State the 4 factors affecting ionistion energy

1. Atomic radius

2. Nuclear charge

3. Shielding

4. Electron pair repulsion

What happens to ionisation energy across a period?

INCREASES- The nuclear charge increases, causing a greater pull on the electrons and therefore more energy is required to remove electrons. There is a decrease between group2 and 3 as the p shells start to fill

What happens to ionisation energy down a group?

DECREASES- due to the shielding of the outer electrons from the nucleus and so the attraction is weaker and they are more easily removed.

Explain atomic emission spectra

Ground state--> absorb heat and become "excited"--> they then become less excited --> they emit energy in fixed amounts (light)

How does ionisation energy show electron configuration?

From right to left you can see the levels which reflect the shells. This shows with group and period an element is in

State the 4 subshells and how many electrons they contain

s- 2 p-6 d-10 f-14

Define orbital

A region within an atom that can hold up to two electrons with opposite spins

What is the shape of the s and p subshells?

s- spherical p- dumbbell

How do electrons fill subshells?

They fill singly then into pairs with opposite spins ("bus theory")

What are the 2 conditions in subshell filling

1. 4s fills and empties before 3d

2. Cu and Cr are 4s1

Which elements are in which block?

Define periodicity

The repeating pattern of physical or chemical properties going across the periods

Explain the trends in melting and boiling points in terms of bonding

Metallic bonding- strong bonds-->high melting and boiling points Ionic bonding- strong bonds-->high melting and boiling points Simple covalent- weak bonds--> low melting and boiling points Macromolecular- strong bonds--> high melting and boiling point

Define ionic bonding

Electrostatic attraction between two oppositely charged ions

Define covalent bonding

Electrostatic attraction between two nuclei and a shared pair of elctrons

Describe the trend of ionic radii down the groups

The radii increases and there are more shells

What is a dative covalent bond?

When the shared pair of electrons in the covalent bond come from only one of the bonding atoms