BIOLOGY Ch.2

anything that takes up space and has mass (dead or living); matter is made up of elements

• is a substance that cannot be
• broken down to other substances by chemical reactions (its made up of one type
• of atom);
• there are 92 elements
• occurring in nature

a substance consisting of two or more diff. elements combined in a fixed ratio ex: NaCl (table salt)

• are those required by an organism only in
• minute quantities like Ca P K S

• smallest unit of matter that still retains the properties of an
• element

no electrical charge

positive charge

negative charge

# of protons

sum of protons plus neutrons in the nucleus

different atomic mass but same element

• one which the nucleus decays
• spontaneously, giving off particles and energy

the capacity to cause change

• charac. Avg. distance and
• energy level; The chem. Behavior of an atom depends mostly on the number of electrons in its outermost shell

means that the atom is not chemically reactive

the 3-D space where an electron is found 90% of the time

sharing a pair of valance electrons by two atoms

two or more atoms held together by covalent bonds

• H:H ( 2 hydrogen covalent
• bond); Molecular formula: H2

• the attraction of particular kind of atom
• for the electrons of a covalent bond

electrons are shared equally

• bond are not shared equally
• Oxygen has a partial negative atom “delta minus”
• Hydrogen has a partial positive atom “delta plus”

charged molecule or atom

positive charged ion

negative charged ion

when cation and anion attract each other. Opposite attraction Ionic compounds or salt: compounds formed by ionic bonds; Most strongest bond is covalent bond

weak chem. Bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

weak and occur only when atoms and molecules are very close together