Chapter 2: Atoms and Molecules

An atom is the smallest particle of an element. It is made up of: protons, neutrons and electrons.
Protons
-Symbol: p
-Has a relative mass of 1
-Has a positive charge
Neutrons
-Symbol:n
-Has a relative mass of 1
-Has a neutral charge (0).
Electrons
-Symbol: e
-Has a relative mass of 1/2000
-Has a negative charge

The nucleus of the atom consists of protons and neutrons. The total number of neutrons and protons is called the nucleon number. Electrons move around the nucleus in fixed orbits.
The number of protons and electrons are actually the same (for example, if the atom has 8 protons, you will know it has 8 electrons). To determine the number of neutrons, subtract the proton number from the mass number to know the number of neutrons the atom has (for example, if the proton number is 17 and there are 8 protons, the number of neutrons is 9).

Examples of positive and negative ions

Initially, I did not know that atoms formed ions, but now I know. Some atoms lose or gain electrons to form the noble gas structure, as it is structurally stable. When an atom loses an electron, it forms a positive ion as there is one less negative charge, thus meaning there are now more protons. When an atom gains an electron, it forms a negative ion, as there is an additional negative charge, thus meaning there are more electrons than protons now.

I've also learnt about molecules are formed from atoms too. Some share electrons with other atoms by combining to form molecules. There are two types of molecules: Molecules of Elements and Molecules of Compounds. Molecules of elements usually consist of a fixed number of the same type of atom. several examples of such molecules are hydrogen gas, oxygen gas and bromine gas. Molecules of compounds are made up of a fixed number of different types of atoms Such examples of these molecules are water, carbon dioxide and ammonia. The Particulate Model of Matter consists of particles but they can be refined to molecules, For example, liquid particles are actually molecules made up of 2 hydrogen atoms and an oxygen atom.

I've learnt how to write chemical formulas, which tells us the type and number of each type of atom present in one molecule of the substance.
Examples:
Water - H20: It's made up of 2 Hydrogen atoms and 1 Oxygen atom
Glucose molecule - C6H12O6: It's made up of 6 Carbon atoms, 12 Hydrogen atoms and 6 Oxygen atoms
I find the knowledge of atoms very useful, as I now know what exactly are matter made up of, and the different types of products formed when atoms are chemically combined together. Before learning this topic, I only knew what is oxygen and carbon dioxide, but not what it is made of. However, now I know, and I feel more knowledgeable.