T1L1 8th grade science

Atom

the smallest particle that can still be considered an element

electron

the negative particle of an atom

nucleus

the dense center of atom

proton

the positively charged particle in the center of an atom

neutron

the particle in the center of an atom that has no charge

atomic number

the number of protons in the nucleus of an atom

isotope

atoms with the same number of protons and different number of neutrons

mass number

the sum of the protons and neutrons in an atom

theory

an explanation that may change with new evidence

What are the 4 parts of Dalton's Theory?

All elements can not be divided

All atoms of the same are the same

An atom of one element cannot be changed into a atom of a different element by a chemical reaction elements cannot be changed

Are formed when more than one element are combined

What did each theorist discover about the atom?

Dalton: 4 principles; Atoms cannot be divided

Thompson: electrons; negative electrons in positive sphere

Rutherford: dense, positive nucleus; protons, mostly empty space

Bohr: electrons move in set orbits around nucleus

Cloud: electrons move in general space "cloud"

Modern (James Chadwick): neutrons added to cloud model

What is the charge of each subatomic particle?

P: +1

E: -1

N: 0

Find the protons, neutrons, and electrons of the isotope Nitrogen-15 and explain how you found each

P: 7 mass # = p+n

E: 7

N: 8