2.5 Simple molecules and covalent bonds
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molecule
a group of atoms bonded together representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
covalent bonds are held together by
weak intermolecular forces
Properties of covalent bonds
low melting and boiling point Poor conductivity insoluble
Covalent bond
When two or more non-metal atoms bond together. The atoms need more electrons to fill their outer shell, so they share to complete
Covalent bonds have these properties because
They have low melting and boiling points because of the weak intermolecular forces holding them together
Compound
A substance is made of two or more elements chemically bonded. It has a definite composition
Mixture
A substance made of two or more substances physically combined. It has variable composition
Element
A substance made of only one type of atom
Proton number/atomic number
Is equal to the number of protons
Electron
A negatively charged subatomic particle that orbits the nucleus
Atom structure
An atom contains a central nucleus containing neutrons and protons surrounded by electrons in shells
Group number
Represents the number of electrons in the outer shell
Mass number/nucleon number
Is equal to the total number of protons and neutrons in the nucleus of the atom
Proton
a positively charged subatomic particle found in the nucleus
Periodic number
Represents the number of electron shells
How to determine the electron configuration
Proton number= Electron number Electron configuration goes up first in 2 in the first shell then the rest 8 2.8.8.8.
Neutron
A neutrally charged subatomic particle found in the nucleus
Calculate the relative atomic mass
It is the sum of (atomic mass x relative abundance) for each Isotope dived by the sum of the relative abundance.(100)
Isotope
Atoms of the same element so they have the same number of protons but with a different number of nuetrons
Why do ionic bonds have these properties
They have high melting and boiling points because they are held together with strong electrostatic forces in lattice of positive and negative ions They can conduct in liquid solutions because the ions become free to move
Ion
An electrically charged particle formed when an atom either loses or gains electrons.
Anion
Negatively charged ion
Cation
positively charged ion
Properties of ionic compounds
High boiling and melting points Good electrical conductivity when aqueous or molten and poor when solid.