Chemistry revision on all topics part 1

Basic atomic structure

Nucleus contains neutrons and protons. The electrons orbit the nucleus. The first shell can hold two electrons and all the others can hold up to eight electrons.

The number of electrons in the outer shell determines which group the element is in.

Atomic number (the small one) is the number of protons in the nucleus of an atom. ( the number of protons equal the number of electrons, that is why an atom has no overall charge.)

The atomic mass is the sum of the protons and the neutrons in the nucleus on an atom.

An atom cannot be broken down further without changing the chemical nature of the substance.

periodic table

Atoms are the basic blocks of all substances and cannot be broken down into simpler substances by chemical means.

Materials made of only one type of atom are called elements, they are all listed in the periodic table by increasing atomic mass.

The periodic table was designed by mendeleev. In developing the modern form of the periodic table he observed recurring patterns in the properties of elements when arranged in order of increasing relative atomic mass and so arranged the elements into groups. He used creative thought to realise that…