Chemistry-Unit1-Fundamental ideas

?

C1. 1.1 Atoms,elements and compounds .

The periodic table is a list of elements.The elements in the periodic table are arranged in columns ,called groups .The elements in a group usually have similar properties .

Each element is made of one type of atom,they are representated by their chemical symbol.Atoms have a tiny nucleus surrounded byelectrons.

When elements react ,their atoms join with the atoms of other elements.

Compounds are formed when two or more elements combine togather.

1 of 5

C1 1.2 Atomic structure

The nucleus at the centre of an atom containstwo types of particles;protons and neutrons.Neutrons have no charge while protons have a positive charge.

Electrons are tiny negatively charged particles that move around the nucleus.An atom has no overall charge.This is because the number of protons is equal to the number of electrons.

All atoms of an element contain the same number of protons.This is the atomic number of the element.Elements are arranged by atomic number .The atomic number is also the nuber of electrons in an atom of the element.

The mass number is the total number of particles in the nucleus of an atom,so it is the number of protons plus the number of neutrons.

2 of 5

C1 1.3.The arrangement of electrons in atoms

Each electron in an atom is in an energy level,they can be represented as shells.

It has only two on the first shell,then eight,then eight again. 2,8,8

Elements in the same group of the periodic table have the same number of electrons in the outer shell.Group 1 has one electron on its outer enery level.

Group 1 elements react quickly with water and with oxygen.

The noble gases are stable.

3 of 5

C1 1.4 Forming bonds

Whe different elements combine they form compounds.

Compounds of metals bonded to non-metals have ionic bonds .Metal elements lose one or more electrons to form positive charged ions.Non-metal atoms gain the electrons to form negatively charged ions.The positive and negative ions are attracted.

When two non-metals combine,their atoms share electrons to form covalent bonds and molecules are formed  

4 of 5

C1 1.5 Chemical equations

Atoms get re-arranged in chemical reactions.The atoms are neither created or destroyed.

The mass of the products is equal to the mass of the reactants.

The equation,in symbols should be balanced.

5 of 5

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Atoms resources »