Chapter 2: Water and Carbon: The Chemical Basis of Life Flashcards
(92 cards)
Atom
Smallest identifiable unit of mass
When the number of protons and electrons in an atom are the same
The charges balance and make the atom neutral
Elements
Fundamental substances that cannot be broken down
atomic number
number of protons in the nucleus of an atom
Mass number
The sum of the protons and neutrons in an atom
Isotopes
Forms of an element with different number of neutrons
atomic weight
average of all the masses of the naturally occuring isotopes based on their abundance in nature.
Radioactive isotope
Nucleus will decay and release energy in the form of radiation.
Orbitals
Electrons move around in this regions and each orbital can hold 2 electrons.
Electron shells
Orbitals are grouped into levels electron shells. Electrons in outershells have more energy than those in the inner shell.
Valence shell
Outermost electron shell of an atom
Valence electrons
An electron in the outermost electron shell. Involved in chemical bonding
Valence
Number of unpaired electrons found in an atom’s valence shell
Chemical bonds
Attractive force binding two atoms together, types being covalent, ionic and hydrogen bonds.
Covalent bond
When two atoms share electrons
Compounds
Atoms of different elements are bonded together.
Electronegativity
A measure of how strongly an atom pulls shared electrons toward itself in a bond.
The number of protons in the nucleus and the distance between the nucleus and valence shell determine the electronegativity.
Basically when you move vertically down on the periodic table elements with more shells have less electronegativity and if you move horizontally to the right, you’ll see higher electronegativities due to more protons.
Oxygen
eight protons and only 6 valence electrons, making it the most electronegative of all elements. Thus it attracts covalently bonded electrons strongly.
nonpolar covalent bond
A bond that involves equally shared electrons is called
H-H and CH4 are examples because they share electrons equally.
Polar covalent bond
Covalent bonds in which electrons are shared unequally between atoms that differ in electronegativity. It results in the more electronegative atom having a partial negative charge and the other atom having a partial positive charge.
Ionic bonds
Electrons are completely transferred from one atom to the other. It gives the 2 resulting atoms a full valence shell.
Cation
Positively charged ion
Anion
Negatively charged ion
Molecular formulas
Indicates only numbers and types of atoms in a molecule