5 Basic Chemistry Atom: Smallest particle an element can be divided into. Parts of the Atom: –Proton: positive charge, in nucleus. –Neutron: no charge, in nucleus. –Electron: negative charge, around the nucleus.
Atom Is now defined as the smallest particle of an element that retains the chemical properties of that element. Nucleus (protons and neutrons) Electrons
The Periodic Table The periodic table is broken down into vertical column called groups or families numbered from left to right (1- 18) and… horizontal rows called periods numbered from top to bottom (1-7)
Types of Elements For the most part you can divide the periodic table into two main parts, Metals and Non-metals.
Metals Metals are located of the left side of the table and make up approximately 88% of all elements. Are generally good conductors of both heat and electricity. Most are solids as well as malleable and ductile.
Nonmetals Are located on the right side of the periodic table and comprise approximately 12% of all elements. Are poor conductors of electricity and heat, tend to be brittle, and are often (though not always) found as gases in nature.
Metalloids Are elements that have some characteristics of metals and also some non-metal characteristics. They are located along the “stair step” line on the right side of the periodic table. All are solids, are less malleable than metals but not as brittle as non-metals. Tend to be semi-conductors of electricity.
Noble Gases Found in group 18 of the periodic table. Generally un-reactive. Gases at room temperature.
16 Basic Chemistry Molecule: –Atoms make up molecules. –Two or more atoms bonded together. One type of atom (ex: O 2 ) Two or more types of atoms (ex: H 2 O)
17 Basic Chemistry Compound: –Atoms make up compounds. –Two or more elements bonded together. Two or more types of atoms (ex: H 2 O)
18 Basic Chemistry Atomic Number: –The number of Protons in the nucleus of an atom of a particular element.
19 Basic Chemistry Atomic Mass: –The number of Protons + the number of Neutrons in the nucleus of an atom of a particular element.
Atomic Number Symbol 6 C Carbon 12.011 [He]2s 2 2p 2 Name Average atomic mass Electron configuration
Isotopes Atoms of the same element (the same number of protons) with different numbers of neutrons. They have identical atomic numbers but different mass numbers.
23 The Four Most Common Elements in Living Matter Atomic Number 6 - Carbon Atomic Number 1 - Hydrogen Atomic Number 8 - Oxygen Atomic Number 7 - Nitrogen
Electron Energy Levels Within the electron cloud, electrons are arranged in “energy levels”. Electrons in each energy level have a specific amount of energy Each energy level can only hold a specific number of electrons. 1 2 4 3
Combinations Few elements exist as independent particles, most substances are made up of combinations of atoms held together by chemical bonds.
Octet Rule “Eight is great” The outer valence shell can hold a maximum of 8 electrons Achieving the maximum number of e- in this valence shell results in a stable “content” atom. 27
Chemical Bond A mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together.
Why Atoms Bond to Other Atoms Most atoms are less stable existing by themselves (they are at a relatively high potential energy). Nature favors arrangements in which potential energy is minimized. Bonding creates more stable arrangements of matter in lower potential energy states. (Mama Nature doesn’t like to sweat!).
Bonding Valence electrons are redistributed. Two main types: Covalent Ionic
Types of Chemical Bonding Ionic vs. Covalent Electrical attraction between cations and anions. Due to gain or loss of electrons (also called electron transfer) between atoms. Sharing of electron pairs between atoms H 2 H 2 O
Animation: Atomic Number, Mass Number PLAY ANIMATION
Ions An ion is an atom or group of atoms with one or more net positive or negative electrical charges. The number of positive or negative charges on an ion is shown as a superscript after the symbol for an atom or group of atoms –Hydrogen ions (H + ), Hydroxide ions (OH - ) –Sodium ions (Na + ), Chloride ions (Cl - )
Electron Dot Notation An electron configuration notation in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element’s symbol.
Lewis Structures Using electron- dot notation to represent molecules. G. N. Lewis 1875 - 1946
Lewis Structures Formulas in which atomic symbols represent nuclei and inner-shell electrons, dot-pairs or dashes represent electron pairs in covalent bonds, and dots adjacent to only one symbol represent unshared electrons.