NOTES Cells Matter Atoms What are cells made

NOTES: Cells – Matter - Atoms

What are cells made of? n Cells are made of different types of matter Matter – anything that has mass & volume n All matter is made out of one or more types of atoms n The atoms combine in different ways to form the matter that makes up cells n

What is an atom? n Atom – the smallest particle of an element Element – a substance that can’t be broken down into simpler substance n Elements are made up of only one type of atom n n The human body is mostly made up of atoms of the elements carbon, hydrogen, oxygen, nitrogen, phosphorous, and sulfur

What is the structure of an atom? n n n Atoms are made up of three subatomic particles: protons (p+), neutrons (n 0), and electrons (e-) Atoms have a positively charged nucleus made up of protons and neutrons Electrons orbit the nucleus in energy levels

Atoms are Neutral n n n Every atom has equal numbers of protons (p+) and electrons (e-) Ex. Oxygen atoms have 8 p+ and 8 e. The negatives cancel out the positives 8 protons n 8 electrons n Total charge n = = = + 8 charge - 8 charge 0

Count the protons and electrons in this fluorine atom

Valence Electrons n n Valence electrons - The electrons in the outer most energy level Valence electrons determine the reactivity of an atom n n Will it bond with other atoms? Ex. Oxygen atoms have 8 electrons n n n 2 in the first level 6 in the second level How many valence e- does an oxygen atom have? n 6

The periodic table gives information about 1 atom of any element

The periodic table gives information about 1 atom of any element n Atomic Number = Number of protons & electrons n n Ex. 1 oxygen atom has 8 protons and 8 electrons Mass Number = Number of protons + neutrons n n n Ex. 1 oxygen atom has 16 protons + neutrons To figure out the # of neutrons, subtract the atomic number from the mass number 16 – 8 = 8 so an oxygen atom has 8 neutrons

How many protons, neutrons, and electrons are in one atom of sodium? n Atomic number is 11, so there are: n n n 11 protons 11 electrons Mass number is 23, so there are: n n 23 – 11 = 12 12 neutrons