Chemistry - ATOMIC STRUCTURE + THE PERIODIC TABLE (C1)

Atoms, elements & compounds -

What is an atom?

The smallest part of an element that can exist.

Atoms, elements & compounds -

What is an element?

A substance made of only one type of atom.

Atoms, elements & compounds -

What is a compound?

A substance made from two / more elements chemically bonded together.

Atoms, elements & compounds -

What is the difference between a compound + a mixture?

Coumpounds have chemically bonded elements in fixed ratios, while mixtures - physically combined + can be separated easily.

Mixtures -

What are the physical separation techniques used for mixtures?

Filtration, crystallisation, simple distillation, fractional distillation, + chromatography.

Mixtures -

How does chromatography separate substances?

Substances - separated based on their different solubilities + how far they travel w/ the solvent on the paper.

Mixtures -

What is the purpose of the baseline in chromatography?

It’s drawn in pencil to mark where the sample is placed; pencil is used because it’s insoluble.

The development of the model of the atom -

Who discovered the electron + when?

J.J. Thomson in 1897.

The development of the model of the atom -

What was the plum pudding model?

A model in which atoms were thought to be spheres of positive charge w/ electrons embedded in them.

The development of the model of the atom -

What experiment led to the nuclear model of the atom?

Rutherford’s alpha particle scattering experiment.

The development of the model of the atom -

How did Bohr improve the nuclear model?

He proposed that electrons orbit the nucleus at specific distances (energy levels).

Relative electrical charges of subatomic particles -

What is the relative charge of a proton, neutron, + electron?

Proton : +1

Neutron : 0

Electron : -1

Relative electrical charges of subatomic particles -

Where are protons, neutrons, + electrons found in the atom?

Protons + neutrons - in the nucleus; electrons orbit the nucleus in energy levels.

Size & mass of atoms -

What is the mass number of an atom?

The total number of protons + neutrons.

Size & mass of atoms -

What is the atomic number of an atom?

The number of protons in the nucleus (also equals the number of electrons in a neutral atom).

Size & mass of atoms -

What is an isotope?

Atoms of the same element w/ the same number of protons but different numbers of neutrons.

Relative atomic mass -

How is relative atomic mass (Ar) calculated?

It’s the weighed average of the mass numbers of an element’s isotopes, taking into account their abundancies.

Electronic structures -

How are electrons arranged in an atom?

In energy levels / shells : 1st holds up to 2, 2nd and 3rd hold up to 8 electrons.

Electronic structure -

What is the electron configuration of oxygen (atomic number = 8)

2,6

Electronic structure -

How does electronic structure relate to the periodic table?

The number of shells = period number; the number of outer electrons = group number.

The periodic table -

How are elements arranged in the modern periodic table?

In order of increasing atomic number.

The periodic table -

What are groups + periods in the periodic table?

Groups - vertical columns; periods - horizontal rows.

The periodic table -

Why do elements in the same group have similar properties?

They have the same number of electrons in their outer shell.

Group 0 - the noble gases -

What are the properties of Group 0 elements?

Inert, colourless gases w/ low boiling points that increase down the group.

Group 0 - the noble gases -

Why are noble gases unreactive?

They have full outer electron shells.

Group 1 - the alkali metals -

What happens to reactivity as you go down Group 1?

It increases.

Group 1 - the alkali metals -

What are some properties of alkali metals?

Soft, low density, react w/ water to form hydroxide + hydrogen.

Group 1 - the alkali metals -

Why do alkali metals become more reactive down the group?

The outer electron is further from the nucleus + more easily lost.

Group 7 - the halogens -

What are halogens?

Reactive non-metals in Group 7 that form -1 ions.

Group 7 - the halogens -

How does reactivity change down Group 7?

It decreases.

Group 7 - the halogens -

What is a displacement reaction involving halogens?

A more reactive halogen displaces a less reactive one from a solution of its salt.