The Periodic table Flashcards
Isotopes
Where the atoms have different masses but the same proton and electron value- a different number of neutrons!
Covalent bonding
Where a pair of electrons is shared between two atoms.
There is a strong attraction between the bonding pair of electrons and nuclei of atoms involved
Giant covalent structures
- Made of millions of atoms bonded together to form a giant structure like diamond, graphite or silicon dioxide.
- They have very high melting points because so many strong covalent bonds have to be broken
Diamond
Used for cutting and jewellery because its hard and abrasive, there are no weak forces in this structure.
Graphite
Used as a lubricant- covalent bonds are strong but the forces of attraction between layers are weak.
Ionic (electrovalent) bonding
Where the electrons are shared between two atoms. Both nuclei are attracted to the same pair
But sometimes one of the atoms is attracted to the electron pair much more strongly than the other. Basically, one atom gives its electrons to the other
Very high melting and boiling points
Metals and non metals form ionic compounds
Cation
Positive ion- metals
Anion
Negative ion- non metals
Formation of Ionic compounds
-The positively charged ions attract the negatively charged ions and arrange themselves into a 3D structure called an IONIC LATTICE
Bonds in Ionic compounds
The ionic bonds between the anions and cations are electrostatic forces of attraction.
The bonds are strong and there are many to break in an ionic crystal. A large amount of energy is required to overcome the forces- high boiling and melting points.
Mg2+O2- will have higher melting points than
Na+Cl-
Simple molecular substances
- At room temperature they are gases and liquids, or solids with very low melting and boiling points.
- This is because the forces of attraction are weak and so little energy is required to break
Protons and electrons
The atomic number is the number of protons in the atoms of the element, equal to the number of electrons. Elements in the same group have the same number of electrons in their outer shell (energy levels). This governs how they will react, so elements in the same group have similar chemical properties though there are differences from the top to the bottom of the group.
Metallic elements
- Group 1 and 2 are METALS
- The group between 2 and 3 are TRANSITION METALS
- The extra 2 rows are RARE EARTH METALS
- Group 3 (minus Boron) are METALS
- Tin and Lead from group IV are METALS
- Bismuth and Polonium from group V and VI are METALS
Boron, Silicon, Germanium, Arsenic and Antlimony are METALLOIDS
Subliming
Solid -> Gas
Group 1- Alkali metals: Elements
Lithium - Less dense than water, floats
Sodium -Less dense than water, floats
Potassium
Rubidium
Caesium
Francium
Group 1- Alkali metals: Trends
- Melting and boiling points are very low (for metals) and get lower as you go down the group.
- Densities tend to increase (though not perfectly)
- Very soft and easily cut with a knife, getting softer as you go through the group.
- All extremely reactive and get more reactive through the group
Group 1- Alkali metals
- Shiny and silver when freshly cut, but tarnish within seconds with air
- React with air to form oxides
- Form compounds where metal has a 1+ ion
- Are mainly white compounds which dissolve to produce colourless solutions
- React rapidly with water to form strong, alkaline solutions of the metal hydroxides and hydrogen, melting and whizzing around on surface
- Can be stored under oil to stop them reacting with oxygen or water vapour or sweat on skin
Transition metals
- Typically all metallic elements
- Good conductors of heat and electricity- workable, strong and mostly with high densities
- With the exception of liquid mercury, they have very high melting points
- Much less reactive and don’t react as easily with air or water
- The majority of transition metal compounds are coloured
Group 7- Halogens: Elements
Fluorine -Gas Chlorine -Gas Bromine -Liquid that easily turns to vapour Iodine -Solid Astatine -Solid
Group 7- Halogens: Trends
- As they get larger through the group, the attraction increases and melting and boiling points increase
- Reactivity falls through the group
- Oxidising agents with oxidising ability decreasing down the group
Group 7- Halogens
- When reacted with metals they produce a wide range of salts
- Non metallic with diatomic molecules (Cl2)
- Poor conductors of heat and electricity and when they are solid, their crystals would be brittle
- Reacts with hydrogen to form hydrogen halides
- Halides are very soluble in water and are covalently bonded
- Displacement reactions
- Coloured poisonous vapours
- Redox reactions
Chlorine
Gas
Pale green
Bromine
Liquid Red brown (evaporates to brown gas)
Iodine
Solid
Black (sublimes when heated to form a purple gas)
Hydrogen Chloride
- Colourless gas
- Dissolves in water and many organic solvents
- A solution of HCl in water is Hydrochloric acid
Hydrochloric acid
- Turns blue litmus red
- Low pH (turns UI red)
- Reacts with reactive metals like Mg, Zn or Fe to form a metal chloride in solution and liberate hydrogen gas
Hydrogen Chloride is acidic in water but not in methylbenzene because:
Hydrogen Chloride molecules don’t ionise when dissolved in methylbenzene. They do when dissolved in water, when hydrogen is given off at the cathode and chlorine is given off at the anode.
HCl (aq) -> H+ (aq) + Cl- (aq)
Group 0- Noble gases: Elements
Helium Neon Argon Krypton Xenon Radon - Radioactive
Group 0- Noble gases
- All colourless gases
- All monatomic, molecules consisting of single atoms
Group 0- Noble gases: Trends
- Densities get higher as you go down the group
- Boiling points get higher as you go down the group
- This is because the attractions between atoms get stronger and the atoms get bigger so more energy is needed to break them apart
- They are generally unreactive
- They don’t form ionic compounds because they don’t form stable ions and are reluctant to form covalent bonds because it costs too much energy
