Atomic Structure and The Periodic Table

What is a element?

A substance made of only one type of element or compound with a fixed melting/boiling point.

What is a mixture?

A combination of two or more substances that are not chemically bonded and can be separated physically.

What is filtration used for?

Separating insoluble solids from liquids.

What is crystallisation used for?

Producing solid crystals from a solution by evaporating the solvent.

What is simple distillation?

Separating a liquid from a solution by evaporation and condensation.

What is fractional distillation?

Separating a mixture of liquids with different boiling points.

What is chromatography used for?

Separating mixtures of dyes or pigments.

Who developed the early periodic table with gaps?

Mendeleev.

Why did Mendeleev leave gaps in his table?

To allow for undiscovered elements and to keep elements with similar properties in the same groups.

What is the modern periodic table based on?

Atomic number.

What are the three subatomic particles?

Protons, neutrons, and electrons.

What is the charge and mass of a proton?

Charge: +1, Mass: 1.

What is the charge and mass of an electron?

Charge: -1, Mass: ~0.

What is the charge and mass of a neutron?

Charge: 0, Mass: 1.

What is the atomic number?

The number of protons in an atom.

What is the mass number?

The number of protons plus neutrons in an atom.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

How is relative atomic mass (RAM) calculated?

(Abundance₁ × Mass₁ + Abundance₂ × Mass₂) ÷ 100.

How are electrons arranged in shells?

In energy levels: 2, 8, 8, etc.

What is the electron configuration of sodium?

2,8,1.

What happens when metals form ions?

They lose electrons to form positive ions.

What happens when non-metals form ions?

They gain electrons to form negative ions.

What does a group on the periodic table represent?

The number of electrons in the outer shell.

What does a period on the periodic table represent?

The number of electron shells.

Why are noble gases unreactive?

They have full outer electron shells.

What are the properties of noble gases?

Unreactive, low boiling points, non-flammable.

What are Group 1 elements called?

Alkali metals.

What happens when Group 1 metals react with water?

They form metal hydroxide and hydrogen gas.

What are the trends in Group 1 as you go down?

Reactivity increases, melting point decreases.

What are halogens?

Non-metal elements in Group 7.

What are the physical states of Group 7 elements at room temperature?

Fluorine: gas, Chlorine: gas, Bromine: liquid, Iodine: solid.

What is the trend in Group 7?

Reactivity decreases, boiling point increases.

What is a halogen displacement reaction?

A more reactive halogen displaces a less reactive halogen from a compound.

Example of a halogen displacement reaction?

Cl₂ + KBr → KCl + Br₂.

What are transition metals?

Elements in the central block of the periodic table (Groups 3–12).

What are the properties of transition metals?

High melting points, good conductors, form coloured compounds, useful as catalysts.

How do transition metals compare to alkali metals?

They are stronger, denser, less reactive, and have higher melting points.