2.5 Simple molecules and covalent bonds Flashcards
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.
Ionic bond
A force of attraction between a cation and an anion (between metals and nonmetals)
What are the similarities between diamond, silicon and graphite
High melting point as a lot of energy is needed to break the strong covalent bonds
Macromolecule
A giant molecule created by atoms covalently bonded to one another
What are the properties and structure of diamond
Made of carbon with 4 covalent bonds
Is the hardest substance on earth because of it using all of its bonds
The properties and structure of graphite
Is made of carbon and each atom makes 3 bonds
Used as a lubricant because the layers in the structure can slide over each other because they are only held together by weak intermolecular forces
Can conduct electricity because of one delocalised electron
The three most know macromolecules
Diamond
Graphite
Silicon
The properties and structures of silicon
Made of silicon and oxygen atoms in the ratio SiO2 in the same structure as diamond
High melting point
Metallic bonding
There are strong electrostatic attractions
between the positive metal ions (cations) and
the negative delocalised electrons
Melting and boiling points in metals
As the metallic lattice is held together by strong electrostatic forces of attraction, metals have high melting points and boiling points.
Electrical conductivity in metals
The delocalised electrons in the metallic lattice are free to move throughout the structure and so metals are good at conducting electricity.
Malleability and ductility of metals
Metals are malleable and ductile
