Chapter 2 - Chemistry

Mass

Matter Have

be broken down chemically

Elements Cannot

protons, neutrons, and electrons

An atom contains..

portons

Atomic Number =

protons + neutrons

Mass Number =

Isotopes

atoms of one element with different neutron counts

Carbon, hydrogen, oxygen, and nitrogen

make up roughly 96% of living matter

Trace elements

such as iron, iodine, and zinc are needed in tiny amounts

deficiency of these elements can still cause disease

Radioactive isotopes

decay at a steady rate and act as tracers

They are used to date fossils and to image tissue in PET scans

electron shells around the nucleus

Electrons occupy..

Valence electrons

the outermost electrons and drive bonding

• a A full blank shell makes an atom chemically stable

Electronegativity

an atom's pull on shared electrons

 

carbon, hydrogen, oxygen, nitrogen

About 96% of living matter is made of just four elements:

 

element identity (atomic number)

The number of protons in an atom determines its:

 

covalent bond

A bond formed when atoms SHARE electrons is a:

ionic

A bond formed when one atom TRANSFERS an electron to another, creating charged ions, is:

 

the slightly positive H of one molecule and the slightly negative O of another

Hydrogen bonds in water form between:

isotopes

Atoms of the same element that differ in their number of neutrons are called:

 

outermost (valence) shell

An atom’s chemical bonding behavior is determined mostly by the electrons in its:

 

polar covalent

A covalent bond in which electrons are shared UNEQUALLY, creating partial charges, is:

 

protons and neutrons

The mass number of an atom equals the sum of its:

 

achieve a stable, filled outer electron shell

 Atoms tend to form chemical bonds in order to:

from unpaired electrons in its valence shell

An atom's reactivity comes from?

the number of bonds formed

The number of unpaired electrons equals

so it forms 4 bonds - CH4

Carbon has 4 unpaired

so it forms 3 - NH3

Nitrogen has 3 unpaired

 so it forms 2 - H2O

Oxygen has 2 unpaired

2 available, so it forms H2S

Sulfur also has 2

molecule

 two or more bonded atoms;

compound

 2+ elements

covalent bond

shares electrons

nonpolar

equal

polar

unequal

ionic bond

transfers electrons, forming charged ions

Bond type

• shapes how a molecule behaves

 hydrogen bond

a weak attraction between polar molecules

Van der Waals forces

leeting attractions between nearby atoms

A molecule's three-dimensional

hape determines its function

• Shape underlies enzyme-substrate and drug binding