The Big Bang, The Atom, The Particle Theory and States of Matter A bit of a review so you don’t feel left behind!

First, let’s talk about how atoms came to exist…

The Big Bang Theory So, our universe went from being very, very small and very, very hot, to the size and temperature of our current Universe! If the universe is expanding, then it must have started off very small, condensed and hot, with only photons (particles of light) It began to inflate (the "Big Bang"), expand and cool. Particles slowed down and quarks and other subatomic particles (the basic components of matter) began to form. As it cooled more, quarks began to form protons and neutrons. It kept expanding and elements kept combining until everything we know today was created It took about a million years to form atoms, and over a billion to form the first stars and galaxies

More About the Formation of Atoms… As photons started to cool, they began to form subatomic particles Subatomic = smaller than the atom (sub = under) A quark is an example of a subatomic particle: it is a fast- moving point of energy. Quarks make up protons and neutrons, which, in turn, make up an atom's nucleus. Each proton and each neutron contains three quarks. Protons contain two 'up' quarks and one 'down' quark while neutrons contain one 'up' quark and two 'down' quarks. Particles called gluons are responsible for binding the quarks to one another. Note: In addition to electrons and quarks, physicists have identified a number of other subatomic particles. Quantum physics describes the subatomic world as one that cannot be depicted in diagrams. Particles are not dots in space (as depicted in this presentation), but are more like "dancing points of energy." Quarks inside a proton

The Structure of an Atom Protons : p+ (positive charge) Neutrons: n° (no charge) Electrons: e- (negative charge) Protons and neutrons are found in the centre of the atom, known as the nucleus. Electrons occupy a space that surrounds an atom's nucleus. We depict this space as rings, but electrons do not “orbit” the nucleus. In reality, scientists cannot tell exactly where an electron is at a given moment or where it is going. These outer rings are actually more like a cloud with electrons zipping around

More About Electron Shells… There is a definite arrangement of the electrons in these shells and a maximum number of electrons possible in each shell. Shell or Orbit Number Maximum Number of Electrons The most electrons possible in the first shell are 2. After the first shell is filled, the second shell starts filling up. The most allowed in the second shell is 8 electrons. After the second orbit or shell is filled, things start to get complicated. The third shell fills until it gets to 8, and then the fourth shell starts adding electrons until it too has 8 electrons. Then the third shell fills until it gets to 18. The valence electrons are the electrons in the last shell or energy level of an atom. They do show a repeating or periodic pattern. The valence electrons increase in number as you go across a period. Then when you start the new period, the number drops back down to one and starts increasing again.

The Periodic Table and Valence Electrons… Outer Orbit +1 e+2 e+3 e+4 e-3 e-2 e-1 eFull Orbits 1 (Period 1) 1H1H 2 He 2 (Period 2) 3 Li 4 Be 5B5B 6C6C 7N7N 8O8O 9F9F 10 N 3 (Period 3) 11 Na 12 Mg 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar

So We Know the Structure of an Atom… What is an Element? Well, let’s go back to the Big Bang –As matter cooled, particles combined to form subatomic particles, and then atoms –Atoms combined to make up elements An element is a substance that is made entirely from one type of atom. –They are “pure” –Ex: hydrogen, helium, gold There are 117 elements known to humans. They are arranged for us to see in the Periodic Table of Elements.

Reading the Periodic Table Atomic number = number of p + in an element Atomic mass = number of p + + number of n° p + = e-

Isotopes Isotopes: Different forms or versions of the same element based on the number of neutrons in the nucleus