Anything that takes up space and mass; organisms are composed of matter
What is an element?
substance that cannot be broken down by other substances by chemical reactions; matter is made up of elements
What is a compound?
a substance consisting of two or more elements in a fixed ratio
What is an atom?
smallest unit of matter that still retains the properties of an element
What forms the atomic nucleus?
protons and neutrons
How do you calculate the mass number/atomic mass of an element?
number of protons + number of neutrons
What is a dalton?
an atomic mass unit (Amu); neutrons and protons are equal to 1 dalton
What is an isotope?
elements with same amount of protons, but different neutrons
What are some uses of radioactive isotopes?
dating fossils, tracing atoms through metabolic processes, and diagnosing medical disorders
What are some of the harmful effects of radioactive isotopes?
radioactive contamination and radiation poisoning
How does an electron vary in their potential energy?
the closer they are to the nucleus, the lower their energy. The further they are from the nucleus, the higher their energy. (further away = energy absorbed, closer = energy lost)
Four major elements in humans?
Carbon, oxygen, hydrogen and nitrogen (contains 96% of our bodies)
What does nitrogen deficiency cause?
loss of growth in plants
What does Iodine deficiency cause?
enlargement of the thyroid glands
What is a covalent bond?
sharing of pair of valence electrons by two atoms (example: H2)
Can form between atoms of same elements or atoms of different elements
What is a molecule?
consisting of two or more atoms held together by covalent bonds (ex: H2)
sharing of ONE pair of valence electrons
sharing of TWO pairs of valence electrons
What is a compound?
a combination of two or more different elements
an attraction between an anion and cation (cat = +, an = -)
strip electrons away from bonding partners (ex: transfer of electron from sodium to chlorine)
After transfer of electron, each atom has a charge (charged atoms = ion) (ex: Na = +, Cl = -)
An atom's attraction for the electrons in covalent bond (more electronegative atom is = more it pulls atom towards it)
High EN = upper right corner of table
nonpolar covalent bond?
atoms share electrons equally (ex: O2)
polar covalent bond?
one atoms more EN, atoms are NOT shared equally (ex: H2O, H = +, O = -)
Importance of weak chemical bonds?
forms a cell's molecules and most of the strongest bonds are in organism. They are ionic bonds and hydrogen bonds. They help to reinforce shapes of larger molecules and help molecules adhere to each other. Also has reversibility advantages.
hydrogen atom is covalently bonded to an EN atom, and is also attracted to another EN atom (ex: H2O --- NH3)
EN partners are usually oxygen and nitrogen atoms
Van Der Waals Interaction?
electrons distributed asymmetrically in molecules and atoms, causes "hot spots" of positive/negative charges (ex: gecko's toe hairs and a wall surface)
Importance of chemical reactions?
reactions CANNOT create or destroy matter, but can rearrange it. It ends up with same # and kinds of atoms (ex: 2H2 + O2 = 2H2O)