Transcript Atomic Mass
2.1 Nature of Matter Atom – atomos – “unable to cut” - basic unit of matter which consists of 3 SUBatomic particle. Proton • Location: in the nucleus (center) • Mass: 1 amu (atomic mass unit) • Charge: Positive (+1) Neutrons • Location: in the nucleus • Mass: 1 amu • Charge: no charge (neutral) Electrons • Location: outside of nucleus in orbitals (electron clouds, energy levels) • Mass: nearly 0 amu • Charge: Negative (-1) Element • Def – a pure substance that consists entirely of one type of atom. • Ex – Gold Rutherford's Experiment: Nuclear Atom Chemical Symbols 6 C 12.011 Atomic Mass Atomic Number 1 – 2 letter chemical symbol Atomic Number – the number of protons found in the atom Atomic Mass – the total number of neutrons and protons in the atom. (Units: amu) Try These 30 11 Na Zn 23 65.5 How many protons? 11 How many protons? 30 How many neutrons? 12 How many neutrons? 35 - 36 Element Name? Sodium Element Name? Zinc Isotopes Def: atoms of an element that have different number of neutrons • All isotopes have the same chemical properties Radioactive Isotopes • Def: isotopes that have unstable nuclei that become stable by releasing radiation – Uses of Radioactive Isotopes • Determine the age of rocks because the nuclei break down at a constant rate. • Treat Cancer Compounds Def: a substance formed by the chemical combination of two or more elements in definite proportions NaCl - Salt H2O - Water C6H12O6 - Glucose Forming Chemical Compounds Ionic Bonds – a bond formed when electrons are transferred from one atom to another. – Ions: atoms of the same element that have lost or gained an electron. – 2-8-8(18) Rule: Elements want to fill their outer shell by gaining or losing electrons. Valence Electrons Valence Electrons: Electrons in the outermost shell of an atom. Ionic Bonding Covalent Bonds Def: A chemical bond that forms when electrons are shared between atoms. Think about Hydrogen Molecule: the smallest unit of most compounds. Animation Covalent Bonds Why does Carbon usually form covalent bonds, instead of ionic bonds? Answer – Outer shell is half full. Van der Waals Forces • Sometimes in covalent bonds the sharing of electrons is not always equal. • Slight attraction between slightly charged regions of a nearby molecules. • A combination of ionic and covalent bonds TED - Gecko Talk Exit Slip • Draw two molecules of water attached to each other, show hydrogen bonds, atoms, and charges. • Boron is atomic #5 and atomic mass is 11 draw this atom, show all subatomic particles. • How many electrons and protons are in Cu 2+ (ion of copper) Atm. #=29 Exit Slip 9/27 • List at least three unique properties of water. • Why would we consider protons to be an atoms identity and electrons to be like the personality of an atom? • Can you explain why one side of a water molecule is slightly positive and the other side is slightly negative?