Atoms, elements and compounds: atomic structure C1

C1 1.1 Atoms, Elements and Compounds

• LO - what are elements made of?
• - how do we represent atoms and elements?
• - what is the basic structure of an atom?
• All substances are made up of atoms
• Substances made up of one atom are elements
• Elements are arranged in columns called groups
• compounds are made up of different types of atoms joined together chemically
• Atoms are made up of a nucleus containing
• - proton (positive charge)
• - neutrons (no charge)
• and the nucleus is surrounded by shells containing
• - electrons (negative charge)
• number of protons = number of electrons
• bottom number - mass number (number of protons and neutrons)
• top number - atomic number (number of protons)

Slide 2

• atoms with the same number of electrons in their outermost shell are in the same group
• first shell - 2
• second shell - 8
• third shell+ - 8
• the atoms in the noble gases (group 0) all have very stable arrangements of electrons

C1 5.5 Ethanol

• Ethanol is a member of the group of organic compounds called the alcohols
• Fermentation of sugar using enzymes in yeast (glucose-->ethanol+carbon dioxide)
• ethanol is the alcohol found in alcoholic drinks
• Ethanol for drinks is made by the fermentation of sugar from plants
• Enzymes in yeast break down the sugar into ethanol and carbon dioxide
• practical:
• you can ferment sugar solution with yeast and test the gas given off
• if you leave the apparatus till next lesson, your teacher can collect some fermented mixture together and distil it to collect the ethanol formed
• We use fractional distillation for the best separation as water and ethanol have a similar boiling point
• ethanol boils at 78 degrees
• the ethanol collected will ignite and burn with a clean blue flame
• Hydration (ethene reacting with steam under pressure in the presence of a catalyst - ethene+steam-->ethanol)
• ethanol for industrial use as a fuel or solvent can be made from ethene gas instead of by fermentation.
• Ethene is made when oil companies crack hydrocarbons to make fuels
• Ethene is the main by-product made in cracking
• Ethene gases can react with steam to make ethanol

C2 1.1

• Elements react together to form compounds by gaining or losing electrons or by sharing electrons
• ionic bonding - in ionic bonding atoms involved lose or gain electrons to form charged particles called ions
• make it so the outermost shell is full
• if the element has lost an electron, it becomes a positive ion
• if the element gains an electron, it becomes a negative ion
• ionic compounds are usually formed when metals react with non metals
• ionic compounds are held together by strong forces of attraction between the oppositely charged ions - this is ionic bonding
• the ionic bonds between the charged particles result in an arrangement of ions called 'giant lattice'

Slide 5

• when non metals react together they form covalent bonds - this is where two atoms share pairs of electrons

questions

• what does ionic bonding involve?
• elements either losing or gaining electrons to form charged particles called ions
• why are ions in a giant lattice held so strongly together?
• the force exerted by an ion on the other ions in the lattice acts equally in all direction

Disadvantages and advantages

• fermentation
• disadv - process carried out in large vats, which have to be left
• (batch process) takes longer
• - produces carbon dioxide (greenhouse gas)
• adv - bio-fuel (renewable)
• hydration
• adv - the process is continuous
• - it produces no waste products
• disadv - relies on crude oil (non-renewable)