S1 Exam

• mass number


  written on top, sum of protons
• atomic number


  written on bottom, sum of protons and neutrons
• isotope


  atoms with the same number of protons ( atomic number) but different number of neutrons
• ion


  positively or negatively charged atoms (lose or gain electrons)
• flame test colour meanings

  metallic elements can be identifies as each line on the emission spectra which is unique to each element

  violet = high energy

  red = low energy
• Bohr model


  electrons revolve around the rucleus in circular orbits
• how do electron shells relate to ground and excited states

  lowest energy cell = inside shell / ground state

  excited state = electron absorbs energy and jumps to a higher energy level
• emission spectra and excited state

  when an electron goes into an excited state and jumps to a higher level, when it returns to the lower energy level it releases energy in the form of light which provides the emission spectra that can be observed
• electron subshell configuration order

  1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
• remembering subshells


  Smart People Don't Forget
• amount in each subshell

  S=2, P=6, D=10, F=14
• condensed electron configuration


  [nearest noble gas symbol] + leftover electron subshell configuration
• Electronegativity


  the ability of an atom to attract electrons

  electronegativity increases across a period and decreases down a group (all roads lead to F)
• what are subshells?


  sub-level of energy within an electron shell
• what is a shell?

  energy level which electrons may occupy in an atom, labeled with a number (n) where n=1,2,3, etc
• what is an orbital?

  a region of space around a nucleus which can contain up to 2 electrons
• alkali metals location


  group 1
• alkaline earth metals location

  group 2
• halogens location


  group 17
• noble gases location


  group 18
• critical element


  elements that are heavily relied on for industry and society that are 'endangered' due to its high demand
• valence electrons


  electrons in the outermost shell
• move down a group

  number of electrons increases, valence electrons have a weaker attraction to the nucleus as they are in higher subshells
• ionic compound


  metallic and non-metallic atoms chemically bonded (positive and negative ions)
• metals


  lose electrons to become positively charged (cations)
• non-metals


  gain electrons to become negatively charged (anions)
• ionic lattice (NaCl)


  - a 3D repeating pattern of positive and negative ions

  - held together by electrostatic forces of attraction between oppositely charged ions (ionic bonds)

  - hard and high melting point due to strong bonds

  - brittle as a strong force can disrupt the layers of the lattice, leading to same charges to be close and repelling eachother
• conductivity requirements


  -charged particles that are free to move (e.g liquids or aqueous solutions)
• molten electric current


  - molten substances conduct electricity due to the movememnt of ions (an electrolyte)

  - positive ions move towards negative end and electrons move towards positive end, creating a current
• solubility


  in ionic compounds that are soluble, ions break away from lattice and mix with water molecules

  like dissolves like (e.g polar dissolves polar)
• insoluble


  in ionic compounds that are insoluble, ions remain bonded in the ionic lattice and do not form a solution
• how is an atom stable

  full outer shell of electrons
• octet rule


  the tendency of atoms to prefer a full outer shell or the tendency for atoms to gain or lose electrons to become stable
• chemical formulas


  charges in superscript swap and move to subscript as products
• polyatomic ions


  2 or more different atoms/elements
• naming ionic compounds


  anions = -ide

  polyatomic anions = -ite or -ate
• SNAPE


  sodium (Na), nitrate (NO3-), ammonium (NH4+), potassium (K+), ethanoate (CH3COO-)

  soluble (aq) -> overrides CHOPS
• CHOPS


  carbonate (CO3^2-), Hydroxide (OH-), Oxide (02-), Phosphate (PO4^3-), sulfide (S2-)

  insoluble (s)
• spactator ions


  can be removed from the equation because they do not participate in the reaction (don't change)
• ionic equation


  equation with spectator ions removed