Atoms are the basis of chemistry. Atoms are the smallest particles of an element that can take part in a chemical reaction and cannot be destroyed without losing its chemical identity. Atoms are composed of three fundamental particles called protons, neutrons and electrons. An atom consists of a small central nucleus, which contains the protons and neutrons. Around the nucleus are electrons, which continuously surround the nucleus (2, 8, 8, 18, 32).
Protons are positively charged particles, electrons are negatively charged particles circling the outer shells and neutrons are neutral.
Compounds are formed when two or more different elements react chemically together, e.g. H2, O2, N2, Cl2, nitrogen oxide, water, nitrogen dioxide and carbon dioxide
An element is a pure substance of one type of atom, e.g. zinc, oxygen, aluminium and copper.
A mixture is a combination or elements or compounds, in which you can separate them again e.g. sand + water, salt + water, and sugar + salt.
An alloy is a metal made by combining two or more metallic elements, e.g. bronze, cupro-nickel, brass, and stainless steel is an alloy of iron and chromium.
Particle theory – Particle theory is a theory of matter that believes matter is made up of particles that are constantly moving around. * Matter is made up of tiny particles (atoms and molecules) * Particles of matter are in constant motion * Particle of matter are held together by strong electric forces * There are empty spaces between the particles of matter that are very large compared to the particles themselves * Each substance has unique particles that are different from the particles of other substances * Temperature affects the speed of the particles. The higher the temperature, the faster the speed of the particles.
Why is an alloy not classed as a compound?
Alloys do not chemically react and there’s a physical mixture, whereas a compound is formed from chemical bonds.
Atomic number = number of protons in a nucleus
Mass number = number of protons & neutrons in a nucleus and mass of nucleus.
Number of protons = atomic number
Number of electrons = number of protons = atomic number
Number of neutrons = mass number – atomic number
The pattern of arrangement of electrons in each shell is referred to as the electron configuration. The outer electron shell in each atom is called the valence shell and the maximum electron population in such as shell is 8.
Atoms or ions with the same number of electrons are said to be isoelectronic
Solids: * Particles in fixed position and less particle movement * Cannot be compressed * Regular lattice arrangement * Definite shape and strong * Strong attractive forces * Very dense
Examples: * Chair * Clothing * Books
Liquids: * Weaker attractive forces * Definite volume * Constant random motion * Particles free to move and quite dense * Little strength
Examples: * Water * Cooking oil * Milk * Mercury (liquid metal at room temperature)
Gases: * No definite shape * Random molecular and atom arrangement and particles free to move around * Low density and no forces of attraction * No strength * Constant rapid and random motion * Can’t be compressed
Examples: * Carbon dioxide * Oxygen * Nitrogen * Helium * Hydrogen
Symbols, Formulae and Equations
First twenty elements on the Periodic Table of Elements: 1. Hydrogen (H) 2. Helium (He) 3. Lithium (Li) 4. Beryllium (Be) 5. Boron (B) 6. Carbon (C) 7. Nitrogen (N) 8. Oxygen (O) 9. Flourine (F) 10. Neon (Ne) 11. Sodium (Na) 12. Magnesium (Mg) 13. Aluminium (Al) 14. Silicon (Si) 15. Phosphorus (P) 16. Sulfur (S) 17. Chlorine (Cl) 18. Argon (Ar) 19. Potassium (K) 20. Calcium (Ca)
Name | Formula | Zinc Oxide | ZnO | Magnesium oxide |