Chapter 1: Atoms and Periodic Table

Question 1

Atomic Number

Answer 1

Number of protons

• atomic number is the smaller number

Question 2

Isotopes

Answer 2

Same element with different number of neutrons

Question 3

Ions

Answer 3

Charged atoms, ions are balanced

• eg. O2- = 2,8
• 0 = 2,6

Question 4

Elements

Answer 4

Not balanced

eg. H= 1
H+ = 2

Question 5

Ionisation Energy

Answer 5

The energy required to remove one valence electron from one mole of an atom in a gaseous state

• Going down group decreases. Outermost electron furhter from nucleus, not attracted as strongly, less energy required to remove.
• Going across a period increases I.E. due to an additional proton being added to the nucleus. As a result, there is a stronger attractive force acting upon the electron
• > therefore requires more energy to remove.

Question 6

Atomic Radius

Answer 6

Radius form the nucleus to the outermost electrons

• moving across a period, atomic radius is decreased due to increasing a proton each time. The electrons feel a stronger attractive force / nuclear charge and therefore pulling them closer to the nucleus, decreasing atomic radius
• increases down a group
• > outer shell e’ in shells progressively further from nucleus due to +ive nuclear charges partially shielded by e’ in inner shells.
• > increased shell level means you have more SHIELDING EFFECT and that decreases electrostatic attraction between valence electrons and nucleus

Question 7

Electronegativity

Answer 7

• A measure of the electron attracting ability of an atom
• Decreases going down a group due to an increasing number of electron shells. Less attractive forces from the nucleus as they are further away
• Increases across a period due to an extra proton being added. Electron shell remains the same which means the nucleus has an increased ability to attract electrons

Question 8

Shielding shells

Answer 8

Electrons in inner shells of atom thought to have shielding effect of positive charge on nucleus

Question 9

2nd ionisation energy

Answer 9

• energy required to remove second electron.
• if in another shell, the electrons are far closer to the nucleus therefore require a much larger amount of energy to remove, hence the large ionisation energy

Question 10

Mass number

Answer 10

• the bigger number

- protons + neutrons

Question 11

of electrons in an atom

Answer 11

• +/- depending on the charge
• relates to # of protons / atomic number
• whereby a negative charge indicates an increase in # added to protons = electrons