Atomic Structure and the Periodic Table

What is the relative mass and relative charge for protons?

1, +1

What is the relative mass and relative charge for neutrons?

1, 0

What is the relative mass and relative charge for electrons?

0, -1

Isotopes

Atoms of the same number of protons but different number of neutrons (same atomic number but different atomic mass)

Molecule

Fixed number of atoms bonded together

What happens when atoms become charged?

An ion is formed

Compound

Two or more elements chemically bonded in fixed proportions.

Fixed proportions

Same ratio of the elements to each other throughout.

Mixture

Different elements that are not chemically bonded.

What is the sum for relative atomic mass (A_r)?

relative atomic mass (A_r) = sum of (isotope x isotope abundance number)/sum of abundances of all the isotopes

Electronic structure

how the electrons are arranged in an atom of that element

What did J.J Thompson discover?

Plum pudding model in 1904, electron in 1897

What is the concept of the plum pudding model?

An atom is a ball of positive charge with negative electrons embedded in it.

What experiment was conducted in 1905 that lead to the nucleus model and by who?

The alpha particle scattering experiment A.K.A the Gold Foil Experiment by Ernest Rutherford and his student Ernest Marsden

What happened in the Gold Foil Experiment?

To their surprise, it resulted in some particles being deflected, some being deflected backwards by the nucleus, and most of the particles passing through empty space.

What did Rutherford come up with based on the results of his experiment?

The mass of the atom is concentrated in the nucleus, the nucleus was positively charged, proved the atom was not a solid, the mass was only in the centre, indicated that the charge was in the centre.

Who revised Rutherford’s nuclear model in 1913?

Niels Bohr

How did Bohr adapt the nuclear model?

He suggested that electrons orbit the nucleus in specific distances (shells), and his theoretical calculations agreed with his experimental calculations.

What conclusion did Rutherford’s further experimentation give?

The positive charge of the nucleus could be divided into smaller particles, discovering the proton which had to be a whole number and all have the same amount of positive charge.

Who proved the existence of neutrons in 1932?

James Chadwick

What is group 0/8 known as?

noble gases

Why are group 0 elements generally stable and unreactive?

They have a full outer shell of electrons.

What are some of the properties of group 0 elements?

• non-flammable

• all exist as single atoms

• colourless gases at room temperature

• B_p increases as you go down the group (because number of electrons+shells increase so greater intermolecular forces need more energy to break them)

What are group 1 elements also known as?

Alkali metals

What are some of the properties of group 1 elements?

• silvery solids that must be stored in oil (they oxidise quickly)

• have low densities (Li, Na, K less dense than water)

• react with water releasing hydrogen

• form hydroxides that dissolve in water to give alkaline solutions

• react with non-metals to form ionic compounds where they form ions with a +1 charge

• B_p and M_p decrease down the group

• reactivity increase down the group

When alkali metals react with water, what happens?

• produces a metal hydroxide + hydrogen gas

• hydroxides formed will dissolve in water to form alkali

When alkali metals react with oxygen, what happens?

They make metal oxides

When alkali metals react with chlorine, what happens?

• produce chlorides

• at room temperature chlorides are white solids

• dissolve in water to form colourless solutions

What are group 7 elements known as?

Halogens, which are non-metal elements that exist as molecules made of pairs of atoms (diatomic molecules)

What are some of the properties of group 7 elements?

• coloured vapours

• form molecular compounds with other non-metallic elements

• react with metals to form ionic compounds where they form halide ions with a -1 charge

• react with non-metals by sharing electrons to form covalent bonds

What are the trends in group 7?

• bond between atoms in molecule are strong, but forces of attraction between molecules are weak

• M_p and B_p increase down the group because molecules get larger, intermolecular forces become stronger and more energy is needed to overcome these forces

• reactivity decreases as you go down the group (atoms get larger, more distance between the outer shell and the nucleus, forces of attraction between nucleus and the outer shell decreases)

When halogens react with metals, what do they form?

metal halides (salts)

What are the properties of transition metals?

• excellent thermal and electrical conductors

• dense, strong and shiny

• their compounds make good catalysts

• can form positive ions with different charges

Compare the properties of transition metals with properties of alkali metals

• both shiny

• good conductors of heat and electricity

• transition metals are less reactive

• transition metals are denser, stronger and harder

• transition metals have higher melting points and boiling points