Which is an example of a mixture

A mixture is two or more substances that have been combined together but each substance is not changed chemically.

Examples of mixtures include:

1. Sea water. This is a mixture of water and various salts.

2. Gunpowder. This is a mixture of potassium nitrate, suilfur and carbon

3. Crude oil. This is a mixture of organic compounds, mainly hydrocarbons.

4. Ink. This is a mixture of colored dyes which can be separated using  chromatography.

5. Dry air. Air is a mixture of nitrogen,oxygen, argon, carbon dioxide, neon and tiny traces of other gases.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.