Structure of Matter The atomic modelDuring the ppt, click the atom for answers to questions& to return back again
Brainstorm . . .What do we know about the structure of an atom?
Brainstorm . . .What do we know about the structure of an atom? comprised of protons, neutrons and electrons protons are positively charged electrons are negatively charged very small mostly empty space protons and neutrons form nucleus electrons found in space surrounding the nucleus
Inside an AtomElectric Relative Position incharge mass (to atom each other) Lithium atom
Inside an Atom Electric Relative Position in charge mass (to atom each other)proton +1 1 nucleus Lithium atomneutron 0 1 nucleus Energy 1 levelselectron –1 1840 around nucleus
Atom Models in History The last 200 years have seen ideas about the atom develop from Dalton’s “indivisible atom” where it is the smallest thing possible; to the discovery of sub-atomic particles (electrons, protons & neutrons); to sophisticated understandings about where these particles are found and how they behave. Each model has allowed hypothesises to be made & predictions tested. This has lead to the development of our knowledge as the technology has improved. video link
Relative Sizes in an Atom atoms are really small!The space electrons occupy is most of the space in an atom. (if the atom was 1 km across, the nucleus would be 1 cm across)
The scanning tunnelling microscope (a recent invention) lets us “see” atoms for the first time.Nickel atoms – showing the regulararrangement of “particles” in a solid Note: the colours are artificially added by computer – nickel atoms aren’t blue!
Atomic Number Lithium atom Atoms from different elements differ in their number of protons. Atomic Number = number of protonsIn a neutral atom, number of protons = number of electrons
Mass NumberMass number = number of protons + neutronsNumber of neutrons = Mass number – Atomic number In this Helium Atom: 4 Atomic number = 2 Mass number = 4 2 He number of protons = 2Helium atom number of electrons = 2 number of neutrons = (4 – 2) = 2
IonsIons are atoms that have lost or gained electrons.Ions have an electrical charge: losing electrons makes positive ions (more protons than electrons) gaining electrons makes negative ions (more electrons than protons) Ex Chlorine atoms gain 1 electron → Chloride ions Cl–1 Ex Sodium atoms lose 1 electron → Sodium ions Na+1 Ex Oxygen atoms gain 2 electrons → Oxide ions O–2 Ex Magnesium atoms gain 2 electrons → Magnesium ions Mg+2