Previously we learned that the average human body has 10,000,000,000,000 (10 Trillion) cells

Q: How many atoms are in one cell?

A: 200,000,000,000,000

100 x more than there are stars in the milky way

2,000,000,000,000,000,000,000,000 200 septillion atoms in the body

Crash Course History of Atomic Structure

The term matter describes all of the physical substances around

us: your table, your body, a pencil, water, and so forth

Anything that has mass and takes up space (has volume)

Made up of different kinds of atoms

Includes all things that can be seen, tasted, smelled, or touched

Does not include heat, sound, or light

Models are often used for things that are too small or too large to be observed or

that are too difficult to be understood easily

In the case of atoms, scientists use large models to explain something that is very small

Models of the atom were used to explain data or facts that were gathered experimentally.

So, these models are also theories

Universe was made of empty space and tiny bits of stuff

Called these tiny bits of stuff atomos

Atomos could not be divided

All elements are composed of indivisible particles (atoms).

Atoms of the same element are the same Atoms of different elements are different. Compounds consisted of atoms of

different elements combined together

Mostly empty space

Small, positive nucleus

Contained protons Negative electrons

scattered around the outside

Used an electric current to learn more about atoms

Noticed “electrons” were attracted to a positive end

Sometimes called the wave model

Spherical cloud of varying density

Varying density shows where an electron is more or less likely to be

Nucleus ◦Protons◦Neutrons

Electrons

Electrons Tiny, very light particles Have a negative electrical charge (-) Move around the outside of the nucleus

Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom 

Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom 

Atomic Number = number of protons

In a neutral atom, the # of protons = the # of electrons

Atomic Mass Number - equal to the number of protons plus neutrons.

Atomic Number: number of protons in an element◦ Zr=40 protons…and

_______electrons

Mass Number: Protons + neutrons◦ H= 1 mass #◦ He=4 mass #