Atomic structure & periodic table

Define atom

The smallest part of an element

Define compound

2 or more elements chemically bonded together which can only be separated by a chemical reaction

Define mixture

2 or more elements/ compounds not chemically bonded together

Ways to separate mixtures

• Filtration

• crystallisation

• Simple distillation

• Fractional distillation

• Chromatography

Don't Try Reading Books Chad!

• John Dalton

  ↳ All matter was made of tiny spheres called atoms which couldn't be divided

• J J Thomson

  ↳ Plum pudding model→ discovered electrons

  ↳ Atom is a ball of positive charge with negative electrons embedded in it

• Ernest Rutherford

  ↳ Alpha particle scattering experiment → nuclear model

• Niels Bohr

  ↳ Electrons orbit the nucleus shells

• James Chadwick

  ↳ Dicovered neutrons

What did the alpha particle scattering experiment prove?

This experiment proved:

• The mass of an atom is concentrated in the nucleus

• The nucleus is positively charged ( positively charged particles were fired and like charges repel)

How small is the radius of an atom?

0.1nm (1 × 10^-10 m)

the radius of a human hair is around (1 × 10^-4 m)

Fill in the blanks

• 1

• 1

• very small

How do you calculate protons and electrons?

Atomic number

How do you calculate neutrons?

Mass number - atomic number

Define isotope

Atoms of the same element with the same number of protons but different number of neutrons

What is the trend in group 1?

Reactivity increases as you go down the group

What is the trend in Group 7

Reactivity Increases as you go up the group

Why? (alkali metals)

✓Atoms get bigger as you go down

✓ Outermost electron is further away from the nucleus

✓ Electrostatic force of attraction between the nucleus and electron is weaker so the electron can be lost more easily

Why? (halogens)

✓ The size of the atom increases as you go down the group

✓ Outermost electron is further from the nucleus

✓ Weaker electrostatic attraction between the nucleus and electron makes it harder for the atom to gain an electron

What are the physical properties of transition metals?

• Conducts electricity

• Shiny

What are the chemical properties of transition metals?

• Produces ions with different charges

• Coloured compounds

• Great catalysts

What are the differences between properties in group 1 and transition metals?

Physical

Transition metals have: higher melting points, higher densities, stronger, harder

Chemical

Group 1: react quickly with oxygen, react vigorously with cold water, and halogens

Why did mendeleev leave gaps in his periodic table?

• Not all elements had been discovered yet and when they were, they filled the gap

• Changed the order based on atomic weight but the knowledge of isotopes explained why it was not always correct to do so

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