C2- structure & bonding Flashcards Preview

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Flashcards in C2- structure & bonding Deck (47)
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1
Q

What is an ion?

A

Ions are electrically charged particles formed when atoms lose or gain electrons.

2
Q

What ions do metal atoms form?

A

Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions

3
Q

What ions do non-metal atoms form?

A

Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions

4
Q

What is the name of the ion formed by fluorine?

A

fluoride.

5
Q

What happens during ionic bonding?

A

When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions. The resulting compound is called an ionic compound. There is a strong electrostatic force of attraction between these oppositely charged ions, called an ionic bond.

6
Q

What is the reaction between sodium and chlorine?

A

sodium + chlorine → sodium chloride

7
Q

What is the reaction between magnesium and oxygen?

A

magnesium + oxygen → magnesium oxide

8
Q

What is the reaction between calcium and chlorine?

A

calcium + chlorine → calcium chloride

9
Q

What is group 1 of the periodic table called?

A

The alkali metals

10
Q

What is group 7 of the periodic table called?

A

the halogens.

11
Q

What is the chemical formula of sodium chloride?

A

NaCl

12
Q

Drawing dot and cross diagrams

A

You know how to do this, but just remember that the two ions need to balance out. So, if one ion has a 2- charge, and the other has a + charge, than you need two +’s.

13
Q

What is the formula of iron (III) hydroxide and why is it written like that?

A

Fe(OH)3 is the formula for iron(III) hydroxide.The formula is written like this because the oxygen and hydrogen atom often act together.

14
Q

How do you work out the formula of a compound?

A

The formula of a compound can be worked out if the ions in it are known. For example, the compound formed from Na+ and SO42- will consist of two Na+ ions to every one SO42- ion so that the compound is neutral overall. The formula is therefore Na2SO4.

15
Q

What is a covalent bond?

A

A covalent bond forms when two non-metal atoms share a pair of electrons. The electrons involved are in the highest occupied energy levels - or outer shells - of the atoms. An atom that shares one or more of its electrons will complete its highest occupied energy level.

16
Q

What are the properties of substances formed by covalent bonds?

A

Covalent bonds are strong - a lot of energy is needed to break them. Substances with covalent bonds often form molecules with low melting and boiling points, such as hydrogen and water.

17
Q

How can you work out the number of covalent bonds a chemical can make?

A

There is a quick way to work out how many covalent bonds an element will form. The number of covalent bonds is equal to eight minus the group number

18
Q

How many covalent bonds can hydrogen, chlorine, oxygen, nitrogen and carbon form?

A

Hydrogen and chlorine can each form one covalent bond, oxygen two bonds, nitrogen three, while carbon can form four bonds.

19
Q

How do you draw the chemical structure of a double and triple covalent bond and what are they?

A

a double covalent bond - meaning they have two shared pairs of electrons - or a triple covalent bond - three shared pairs of electrons. A double covalent bond is shown by a double line, and a triple bond by a triple line.

20
Q

What is the chemical formula of hydrogen chloride?

A

HCl

21
Q

What is the chemical formula of ammonia?

A

NH3 (little 3)

22
Q

What is the chemical formula of methane?

A

CH4 (little 4)

23
Q

What are simple molecules?

A

These contain only a few atoms held together by strong covalent bonds.

24
Q

What are the properties of simple molecules?

A

Low melting and boiling points - This is because the weak intermolecular forces break down easily.
Non-conductive - Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge.

25
Q

What is it that breaks down in simple molecules?

A

When one of these substances melts or boils, it is these weak ‘intermolecular forces’ that break, not the strong covalent bonds.

26
Q

What are macromolecules?

A

Macromolecules have giant covalent structures. They contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds. Their atoms are arranged into giant lattices, which are strong structures because of the many bonds involved.

27
Q

What is diamond and what are its properties?

A

Diamond is a form of carbon in which each carbon atom is joined to four other carbon atoms, forming a giant covalent structure. As a result, diamond is very hard and has a high melting point. It does not conduct electricity.

28
Q

What is graphite and what are its properties?

A

Graphite is a form of carbon in which the carbon atoms form layers. Each carbon atom in a layer is joined to only three other carbon atoms.The layers can slide over each other because there are no covalent bonds between them. This makes graphite much softer than diamond. It is used in pencils and as a lubricant. Graphite conducts electricity

29
Q

What is Silica, and what are its properties?

A

Silica, which is found in sand, has a similar structure to diamond. It is also hard and has a high melting point. However, it contains silicon and oxygen atoms instead of carbon atoms.

30
Q

Name three differences between HDPE and LDPE?

A

There are many branches on the polymers of LDPE, but not on HDPE. LDPE is quite weak, whereas HDPE is quite strong. The maximum usable temperature for LDPE is 85, and for HDPE it is 120

31
Q

What are thermosofting polymers?

A

Thermosoftening polymers soften when heated and can be shaped when hot. The shape will harden when it is cooled, but can be reshaped when heated up again. Poly(ethene) is a thermosoftening polymer. Its tangled polymer chains can uncoil and slide past each other, making it a flexible material.

32
Q

What are thermosetting polymers?

A

Thermosetting polymers have different properties to thermosoftening polymers. Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily

33
Q

What are the properties of ionic compounds?

A

Ionic bonds are very strong so a lot of energy is needed to break them. Ionic compounds contain many of these strong bonds so they have high melting and boiling points.Ionic compounds conduct electricity when they are dissolved in water or when they are melted. This is because their ions are free to move and carry the current. However, ionic compounds do not conduct electricity when they are solid. This is because their ions cannot move around in their lattice structure.

34
Q

What are the properties of metals?

A

Metals are malleable - they can be bent and shaped. This is because they consist of layers of atoms. These layers can slide over one another when the metal is bent, hammered or pressed. Metals are good conductors of electricity and heat. This is because the free electrons can move throughout the metal.

35
Q

What is the structures of metal?

A

Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.

36
Q

What are alloys?

A

An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.

37
Q

Why are alloys harder than pure metals?

A

Alloys contain atoms of different sizes. These different sizes distort the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.

38
Q

What are shape-memory alloys and what are there uses?

A

Shape memory alloys can return to their original shape after being bent or twisted. Nitinol is a shape memory alloy made from nickel and titanium. It is used in dental braces and spectacle frames.

39
Q

What is a nanometre?

A

A nanometre, 1 nm, is one billionth of a metre (or a millionth of a millimetre).

40
Q

How large are nanoparticles?

A

Nanoparticles range in size from about 100 nm down to about 1 nm. They are typically the size of small molecules, and far too small to see with a microscope.

41
Q

What are the properties of nanoparticles?

A

Nanoparticles have a very large surface area compared with their volume, so they are often able to react very quickly. This makes them useful as catalysts to speed up reactions.Nanoparticles also have different properties to the same substance in normal-sized pieces.

42
Q

What may nanoscience lead to the development of?

A

New catalysts
New coatings
New computers
Stronger and lighter building materials
Sensors that detect individual substances in tiny amounts
New cosmetics such as sun screen and deodorants.

43
Q

What are the properties of graphite?

A

Graphite is a good conductor of heat and electricity. This is because, like metals, graphite contains delocalised electrons. These electrons are free to move through the structure of the graphite.Graphite is soft and slippery because there are only weak intermolecular forces between its layers.

44
Q

What are fullerenes?

A

These are cages and tubes with different number of carbon atoms. Buckminsterfullerene is one type of fullerene. Its molecules are spherical and contain 60 carbon atoms.

45
Q

What can fullerenes be used for?

A

Fullerenes may be used for drug delivery systems in the body, in lubricants and as catalysts.

46
Q

What are nanotubes?

A

The tube fullerenes are called nanotubes.

47
Q

What can nanotubes be used for?

A

These are very strong. They are useful in reinforcing structures where lightness and strength are needed - for example, in tennis racket frames.

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