Chemistry chapter 2

• What is an atom?

  a positively charged nucleus ( consisting of protons and neutrons ) surrounded by negatively charged electrons
• What is the relative charge of a proton, neutron and electron?

  proton: +1 , neutron: 0 , electron: -1
• What is the relative mass of a proton, neutron and electron?

  proton: 1, neutron: 1, electron: 0.0005
• How tiny is the nucleus in comparison to the atom?

  about hundred thousandth of the diameter (which is 1 x 10^-10m) of the atom
• What are molecules?

  groups of atoms held together by covalent bonds therefore larger in size
• How do simple molecules differ from molecules?

  they are tiny in size as bonds between them are generally similar to atomic diameter
• What is the mass number?

  total number of protons and neutrons
• What is the atomic number?

  Number of protons
• What are ions?

  an atom with positive or negative charge
• How are positive ions formed?

  Positive ions form when atom lose electrons ( more protons than electrons )
• How are negative ions formed?

  Negative ions form when an atom gains electrons ( more electrons than protons )
• What are isotopes?

  different forms of the same element where atoms have the same number of protons but different number of neutrons
• What does the column in a periodic table tell us about the elements?

  the group which each element correspond to allows us to identify the number of electrons they have in their outer shell
• How many electrons will elements in group 1, group 7 and group 0 have?

  group 1 will have 1 electron in outer shell, group 7 will have 7 electrons in outer shell, group 0 is the only exception with 8 electrons in outer shell
• What do the rows of the periodic table tell us about each element?

  how many electron shells each element has occupied ( starts with 2 )
• How does the periodic table help predict the reactivity of the elements?

  Elements in the same group ( therefore same number of electrons in outer shell ) will react in similar ways

  In group 1, the more shells an element has, the more reactive it will be

  In group 7, an increasing number of shells make the element less reactive
• What are metals and non-metals?

  Metals are elements that react by losing electrons (forming positive metal ions)

  Non-metals are elements that react by gaining electrons (forming negative metal ions)
• How does the positioning of the metals and non-metals in the periodic table tell us whether they lose or gain electrons?

  Metals are positioned on the left - they want to lose electrons because they don't have many electrons in their outer shell

  Non-metals are positioned on the right - they want to gain electrons to fill the almost-full outer shell
• What are the properties of metals?

  Shiny appearance, good conductors of heat and electricity, high densities, high boiling and melting points ( solids at room temp ) , reactivity increases as you go down the table, form compounds with ionic or metallic bonds
• What are the properties of non-metals?

  Dull looking, poor conductors of heat and electricity, low densities, low boiling and melting points ( gases and liquids at room temp ), reactivity decreases as you go down the table, form compounds with ionic or covalent bonds
• What are the properties of group 0 elements?

  gases at room temperature with low melting and boiling points ( melting and boiling points increase as you go down the group )
• What are the group 1 elements?

  lithium, sodium, potassium, rubidium, caesium, francium
• What are the characteristics of group 1 elements?

  known as alkali metals ( react vigorously with water ) all have one electron in their outer shell making them very reactive, have similar chemical properties
• What are the properties of group 1 elements?

  as you go down the group --> increasing reactivity, lower melting and boiling points, higher relative atomic mass, higher density, decrease in hardness
• Why do melting points and boiling points decrease as you go down the group 1 elements?

  outer electron of each atom is free to move ( delocalised), strong attraction with positively charged nuclei

  as you go down the group --> atoms get bigger, more outer shells, increased distance from nuclei so attractions gets weaker, les energy required to break the bonds
• How do group 1 metals react with air?

  shiny when first cut but quickly react with oxygen in moist air and tarnish as metal oxide is formed

  as you go down the group, reactivity increases so tarnish quicker
• How do group 1 metals react with water?

  as you go down the group, elements become more reactive and may even explode

  Lithium --> takes longest to react, turns water purple, fizzing until disappears

  Sodium --> fizzes rapidly around surface and may ignite

  Potassium --> reacts vigorously, burns with lilac flame
• How do group 1 metals react with chlorine?

  react vigorously when heated in chlorine gas to form white crystals called metal chlorides --> gets more vigorous as you go down the group since reactivity increases
• What are the group 7 elements?

  fluorine, chlorine, bromine, iodine, astatine
• What are the characters of group 7 elements?

  known as halogens, 7 electrons in their outer shell so similar chemical properties,

  diatomic molecules --> sharing one pair of electrons in covalent bonding gives both atoms full outer shell
• What are the properties of group 7 elements?

  non metals, become less reactive down the group

  as you go down the group --> melting and boiling point increases ( because increase in number of shells in each atom ) so more electrons mean greater intermolecular forces ( more energy required to overcome them )
• What is the state of Fluorine at room temp?

  highly reactive, toxic, pale yellow gas
• What is the state of Chlorine at room temp?

  fairly reactive, poisonous, green gas
• What is the state of Bromine at room temp?

  poisonous, red-brown liquid
• What is the state of iodine at room temp?

  dark grey, crystalline solid
• What do halogens form when reacting with alkali metals?

  halogens react vigorously with alkali metals (group 1) to form salts called metal halides

  halogens higher up in group 7 react more vigorously with alkali metals as they are more reactive
• What is a displacement reaction in terms of group 7 elements?

  displacement reaction is when a more reactive metal displaces a less reactive metal from a compound

  e.g. chlorine is more reactive than bromine ( higher up in group 7 ) so displaces bromine in aqueous solution
• What are the properties of ionic compounds?

  high melting and boiling points due to strong forces of attraction between ions

  dissolve easily in water because charges allow them to interact with water molecules

  ions separate and are free to move so carry electric current however when solid they cannot because ions are held in fixed positions