exam 1 Flashcards
(104 cards)
Matter
Anything that takes up space & has mass.
Elements
Cannot be broken down into other substances by chemical reactions.
Compound
2 or more elements combined in a fixed ratio.
e.g.: Na + Cl NaCl (table salt)
4 elements that make up 96% of living matter
Carbon - C
* Oxygen - O
* Hydrogen - H
* Nitrogen – N (often limiting in plants)
CHNOPS
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, Sulfur
Atoms
the smallest unit having the properties of an element
Composition of atoms
in the nucleus there is protons and neutrons. Protons- positively charged
neutrons- no charge
Electrons- (negatively charge) orbit nucleus in electron cloud
Atomic number vs. Atomic mass
Atomic number = number of protons
Atomic mass = number of protons + neutrons
Isotopes
different atomic forms of same element. Same number of protons BUT different numbers of neutrons.
Electrons energy levels
Lowest energy: shell closest to the nucleus.
Electron can absorb energy, “bumping” electron into a higher shell.
Electron will then give up energy by “falling” back to its original level/shell.
Electron shells
1st shell holds 2 electrons (1s orbital)
2nd shell holds 8 electrons (2s + 2p orbitals)
3rd shell holds 8 electrons (2s + 2p orbitals)
Valence electrons and valence shell
electrons located in the valence shell (the outermost shell).
Chemical bonds
The exchanging and sharing of electrons between atoms.
Covalent bonds
Sharing of a pair of valence electrons between 2 atoms
Electronegativity
affinity for electrons, an inherent property of each type of atom. Electronegativity increases bottom to top in a column and left to right in a row.
Polar covalent bond
occur between elements with different electronegativity. Water molecule.
Nonpolar covalent bond
occurs between elements that have the same electronegativity. Much weaker than covalent bonds.
Ionic bonds
attraction that occurs between oppositely charged ions. One atom actually strips an electron completely away from its partner because their electronegativity is so different
Cation
Positive charge ion
anion
Negative charge ion
Hydrogen bonds
The attraction between a partial positive and partial
negative is a hydrogen bond.
Van Der Waals
a weak attraction when atoms are so close that outer electron shells barely touch…Hot spots of + or - charge
Cohesion
Hydrogen bonds cause water molecules to stay close to each other
Surface tension
a measure of how difficult it is to stretch or break the surface of a liquid