Chapter 3
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There are 3 sub-atomic particles
• protons • neutrons • electrons
These sub atomic particles are found in the nucleus
• neutrons - protons
State the relative charges and approximate relative masses of protons, neutrons and electrons
Protons: +, 1 Neutrons: 0, 1 Electrons: -, 0
Define proton number
The number of protons in the nucleus of an atom
Define nucleon number
The total number of protons and neutrons in the nucleus of an atom
Define isotopes
Atoms of the same element which have the same proton number but a different nucleon number
State the two types of isotopes
Radioactive and non-radioactive
Why do isotopes have the same properties?
It is because they have the same number of electrons in their outer shell.
State one medical and one industrial use of radioactive isotopes
To kill cancer cells with radiotherapy - Cobalt_60 Generates x-rays for fracture diagnosis - Iridium_192 Diagnosis of anaemia - Iron_59 Power source for space shuttles - Plutonium_238 Detects presence of explosives in airline luggage - Californium_252 Produces alpha radiation for use in smoke detectors - Americium_241
Describe the differences between elements, mixtures and compounds, and between metals and non-metals
Elements: An amount of substance that contains only one type of atom, including isotopic variations. Mixtures: When two or more substances are found together but are not chemically bonded to each other. Compounds: Made up of 2 or more atoms of different elements that are joined together through chemical bonds. Metals: Large atomic radii, can conduct heat and electricity, high range of melting points, malleable and ductile, shiny Non-metals: Small atomic radii, can not conduct heat and electricity, generally low melting point, brittle, dull
Describe an alloy
A mixture of a metal with other elements. Created by mixing two melted metals and allowing them to cool down.
Describe the formation of ions
Ions are formed through the loss or gain of electrons.
Describe the formation of ionic bonds between elements from Groups I and VII
Elements that are metal get rid of their outermost electrons while non-metals try to gain more electrons in their outermost shell. This is to achieve a noble gas configuration to become stable. To do this, an electron is transferred from a metal element to a non-metal element.
Cations and anions
Positive ions are cations, negative ions are anions. Most metals are cations and most non-metals are anions.
Why don’t metals gain electrons to achieve a noble gas configuration?
This is because it would take much more energy to do so instead of just losing electrons.
Describe the formation of ionic bonds between metallic and non-metallic elements
Due to an electron transfer, there is a strong force of attraction between metals and non-metals
Describe the lattice structure of ionic compounds
A regular arrangement of alternating positive and negative ions
Why are ionic lattices formed?
This is because of the strong electrostatic forces between each atom
What is Valency?
The number of electrons either gained or lost during ionisation.
Describe the formation of single covalent bonds in H2, Cl2, H2O, CH4, NH3 and HCl
The sharing of pairs of electrons leading to the noble gas configuration
Describe the differences in volatility, solubility and electrical conductivity between ionic and covalent compounds
Covalent compounds: High volatility, low solubility and no electrical conductivity. Ionic compounds: Low volatility, High solubility and only electrical conductivity when molten or in a solution.
What is a covalent bond?
A force of attraction between non-metals through the sharing of an electron.
Describe the electron arrangement in more complex covalent molecules such as N2, C2H4, CH3OH and CO2
They are more complex as they have double, triple etc bonds.
Explain the differences in melting point and boiling point of ionic and covalent compounds in terms of attractive forces
The melting point and boiling point of ionic compounds are higher because they have a much stronger attraction and intermolecular forces in their ionic lattices and therefore require much more energy in order to be separated.