Introduction To Quantitative Chemistry

Explain why noble gases are described as stable.

The noble gasses all have a full outer shell so they do not need to react to gain, lose or share electrons.

Describe how elements are arranged in the periodic table.

Order of increasing atomic (proton) number

State the pH range of alkalis.

8-14

Alkali metals have… and are…

1 electron in their outer shell… very reactive and readily react with other elements to form compounds.

As you move down the group, alkali metals get…

get more reactive because they lose their one outer electron more easily.

The electron is attracted to the…

positively charged nucleus. The stronger the attraction, the less likely this electron will be lost.

Which group contains the alkali metals?

Group 1

State two properties of the alkali metals

• are soft (they can be cut with a knife)

• have relatively low melting points

Explain why the alkali metals have this name.

when they react with water they form alkalis.

Potassium reacts with water, state two observations.

• lilac flame

• hydrogen gas

Alkali metals if left out in air become less shiny. Why?

The alkali metals react with oxygen in air.

The alkali metals move quickly around the bowl of water. Why?

The hydrogen gas produced pushes (or propels) the metal around.

Potassium burns with a lilac flame. Why?

The hydrogen gas produced by the reaction burns

The alkali metals float on water.

They are less dense than water

Elements in Group 7 of the Periodic Table are called the…

Halogens

Halogens are…

non-metals and consist of diatomic molecules

Diatomic molecules are…

molecules made of two atoms chemically bonded together.

In group 7, the further down the group an element is, the higher its… why?

melting point and boiling point. This is because, going down group 7:

• the molecules become larger

• The forces between the molecules become stronger

• more energy is needed to overcome these forces

halogens… in reactivity as you

go down the group, because …

decrease… The further the outer shell is from the nucleus, the harder it is to attract a negatively charged electron.

When a halogen reacts with metal, the product is a compound called…

a metal halide.

lithium + chlorine →

lithium chloride

When a halogen reacts with hydrogen, the product is a compound called a…

hydrogen halide.

hydrogen + chlorine →

hydrogen chloride

The transition metals are in the…

central part of the periodic table

Compared to other metals, transition metals have…

• higher melting points

• higher densities

• greater strength

• greater hardness

Just like most other metals, transition metals are usually…

• Solid at room temperature

• Shiny

• Good conductors of electricity

Many transition elements can form…

ions with positive charges.

An ion is a…

charged atom or molecule. Ions are formed when electrons are lost or gained.

A catalyst is a…

substance that increases the rate of a chemical reaction.

One order of magnitude means…

10x

Relative Formula Mass

For compounds (different elements combined together chemically) we can calculate the relative formula mass or Mr.

This is calculated by adding up the relative atomic masses of the all the atoms in the formula.

percentage by mass equation

% by mass = A_r x number of atoms in a compound / M_r of the compound