Unit 1: Chapter 2 - The Periodic Table - Bonding and Structure Flashcards
in metallic bonding what are the atoms arranged in?
In metallic bonding the atoms are arranged in a crystalline structure where the positive atoms are surrounded with a SEA OF ELECTRONS.
What is it that holds the structure in place, in metallic bonding?
It is the ELECTROSTATIC ATTRACTION of positive atoms and negative outer electrons that hold the structure in place.
Why can metals be bent and what is this property called?
As the atoms are all the same size, and in an ordered structure, metals can be bent, a property known as malleability.
What is covalent bonding?
Covalent bonding is when atoms share pairs of electrons. The covalent bond is a result of two
positive nuclei being held together by their common attraction for the shared pair of electrons/the electrostatic attraction between the positive nuclei and the negative shared pair of electrons.
What is ionic bonding and what does this create?
Ionic bonds are the electrostatic attraction between positive and negative ions. Ionic compounds form lattice structures of oppositely charged ions.
What is the London Dispersion Forces of attraction between?
Between monatomic atoms and small discrete molecules.
What is the force caused by in London Dispersion Forces?
The force is caused by uneven distribution of the constantly moving electrons around the nuclei of the atoms. The atom has an electron deficient side which is very slightly positive (δ+) and is attracted to a side of another atom which has an excess of electrons which is very slightly negative (δ-) . THIS IS CAUSED BY THE MOVEMENT OF THE ELECTRONS IN ATOMS.
Are London Dispersion Forces easily broken and what element and compounds can they be found?
Yes. Elements and compounds with very low melting and boiling points.
What group number are the halogens and what properties do they have?
Group 7 and they kill bacteria.
What group are the alkalis and what do they all have in common?
Group 1 and they are all very reactive.
What accounts for higher melting and boiling points within London Dispersion Forces?
AS you go down a group for instance group 7, the molecules get bigger with more electrons meaning the negative dipoles are stronger thus the melting and boiling points increase.
What does the London Dispersion Forces cause the formation of?
TEMPORARY DIPOLES.
What are the diatomics?
Hydrogen, nitrogen, oxygen, fluorine, chlorine, iodine, bromine.
What are diatomics?
Molecules composed of only two atoms.
What are known as the covalent molecular structures?
Hydrogen, oxygen, nitrogen, phosphorus, sulphur, the halogens, chlorine nanotubes and the fullerenes.
Give an account of the covalent molecular of oxygen?
Oxygen is vital to sustain life and takes part in many chemical reactions such as combustion and corrosion. Oxygen atoms are held together by two strong covalent bonds (double bond). Similar to nitrogen the oxygen molecules are held together by weak London Dispersion Forces.
Give an account of the covalent molecular of Fullerenes?
Fullerenes were discovered in 1985 in ‘ soot ‘ the fullerenes are discrete, covalently bonded molecules of carbon with the smallest being C60. Named after the American architect Buckminster Fuller who designed the Geodesic Dome which has a similar shape. The
‘ buckyball ‘ has a spherical shape which contains only carbon atoms which are bonded in 5 and 6 members rings.
How can London Dispersion Forces increase in strength at lower temperatures?
London Dispersion Forces increase in strength at lower temperatures due to a decrease in molecular vibration.
What is not affected in the London Dispersion Forces wether the covalent molecules are solid liquid or gas?
The strong covalent bond holding the atoms together are not affected.
What are elements that can bond in a covalent network structure?
Boron Carbon and Silicon.
In their natural state what do the elements boron, carbon and silicon comprise of?
A vast three dimensional lattice structure where each atom is bonded by strong covalent bonds in a continuous network.
Give an account of the covalent network structure of Silicon?
Silicon rarely occurs as the pure element in nature. 90% of the Earth’s crust is composed of silicates, making silicon the 2nd most abundant element in the Earth’s crust after oxygen. It has a covalent network structure, medium reactivity and is best known as a semiconductor used in the ‘silicon chip’ in computers.
Give an account of the covalent network structure of Carbon?
Carbon is a part of the fullerenes, which are small discrete molecules. Other forms of carbon are diamond, graphite and sugar charcoal, (normal charcoal has impurities) and have large covalent network structures.
Give an account of the covalent network structure of Diamond?
Diamond is the hardest substance on earth, it has a giant covalent network structure with each carbon bonded to four other carbons. It does not conduct electricity, is unreactive and is used as jewellery and as a cutting tool. A process to make synthetic diamond has been discovered which requires high temperatures and pressure.
