Matter The “stuff” of the universe Anything that has mass and takes up space Held together by energy Atoms provide the mass

Models of the Atom Planetary Model – electrons move around the nucleus in fixed, circular orbits Orbital Model – regions around the nucleus in which electrons are most likely to be found

Included in Appendix 2 of your text

Electron Energy Levels (Shells) Valence electrons

Fig 2.6

Transfer of Electrons oxidation: loss of an electron reduction: gain of an electron

Composition of Matter Elements – unique substances that cannot be broken down by ordinary chemical means Atoms – more-or-less identical building blocks for each element

Identification of Elements Mass number – equal to the mass of the protons and neutrons Isotope – atoms with same number of protons but a different number of neutrons Radioisotopes – atoms that undergo spontaneous decay called radioactivity

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Chemical Bonding Determined by the character of the electrons 1. sometimes ions are formed 2. cations 3. anions Molecules are formed by the interaction of valence electrons Bonds are simply attractive forces (nothing physical) Atoms bond because they want to “fill their valence shells.”

relatively strong easily dissociate in H 2 O based on the attraction of oppositely charged ions Ionic Bonds:

Covalent Bonds:

Polar covalent bonds

2. very weak 3. found in: liquid water macromolecules Hydrogen Bonds: