Atom: basic building blocks of matter Structure: Nucleus Electron Proton Neutron

Definitions: Nucleus- center of atom, contains protons and neutrons  Protons: positive charge (+)  Neutrons: neutral charge (=)  Electrons- negative charge (-), orbit in energy levels on outside of atom

Location of Subatomic Particles nucleus Protons Neutrons electrons

Energy Levels-  Orbit around nucleus  Forms “shells” around nucleus  Electrons fill the shells from the inside out 1st 3rd 2nd N 1 st level: max of 2 electrons 2 nd level: max of 8 electrons 3 rd level: max of 18 electrons

Elements: all the same type of atoms bonded together Can’t be broken down into simpler substances 90 occur naturally Others are man-made 25 essential to living organisms 99% of living organisms are made of C,H,O,N

Isotopes- atoms of the same element with different number of neutrons in the nucleus Symbols- shorthand abbreviations for elements  Rules:  First letter always capital  Second letter always lower case  Every element has a different symbol  Ex’s: Mg N O Na C Cl

Periodic Table  Elements are arranged in columns known as a family or group  Families have similar properties because the outer shell of the atoms have the same number of electrons

Atomic Mass on the Periodic Table 11 Na Atomic Number Symbol Atomic Mass

Atomic Number & Mass Meanings Atomic number = the number of protons and the number of electrons (this will be equal for stable elements.) Atomic mass – the atomic number = the number of neutrons (round to whole number)

Molecule/Compound: a substance that contains different elements bonded together Formula- a set of symbols that show the type of elements and the ratio in which they combine  Ex’s: CO 2 H 2 O

Subscript- number after element indicating the number of atoms present Coefficient- number in front of the formula indicating the number of molecules present  Ex’s: 3H 2 O – 3 molecules of water 6NH 4 – 6 molecules of ammonia

Water: (H 2 O) One of the most important compounds in living organisms Makes up 70-95% of most organisms

Properties of Water 1. Polar Molecule: it has an unequal distribution of charge. The oxygen side has a slightly negative charge, so ionic compounds dissolve easily in water.

2. Resists temperature change 3. Expands when it freezes 4. High surface tension because the polar molecules are attracted to each other and form a slight film on the surface. 5. Capillary action, which means, plants can carry water up thin tubes.

Organic & Inorganic Molecules Organic molecules- contain carbon (C) Inorganic molecules- do not contain C Which of the following are organic? H 2 O NaCl C 6 H 12 O 6 CaCO 3

Living Organisms are made up of 4 abundant and 9 less abundant elements: C Hopkins café Magic Salt (NaCl) *C= carbonCa= calcium *H= hydrogenFe= iron *O= oxygenMg= magnesium P= phosphorusNa= sodium K= potassiumCl= chlorine I= iodine *N= nitrogen*makes up 99.3% of a S= sulfur living organism

Bonding Covalent bond- chemical bond when two atoms combine sharing electrons - Examples: sugars, fats, & proteins

Ionic bond- bond formed by the mutual attraction of two ions of opposite charge  Examples: salt (NaCl) Na+ Cl-  Hydrogen bond- electrical attraction between a slightly negative atom and a slightly positive atom. Very weak so molecules must be close to experience this attraction.  Examples: water (H 2 O)

Chemical Equations Reactants- substances that undergo a chemical reaction Products- substances formed by the chemical reaction *Chemical equations must be written so they are balanced! Atoms are neither created nor destroyed during chemical reactions.