Section 1
Smallest part of an element
Atom
# of protons in an atom's nucleus
Atomic Number
Russian chemist presented a way to organize all the known elements
Dmitri Mendeleev
Particles with an electric charge of 1-
Electrons
The small, positively charged center of an atom
Nucleus
number of protons + number of neutrons =
Mass number
organized list of all known elements that are arranged by increasing atomic number and by changes in chemical and physical properties
Periodic table
Particles with an electric charge of 1+
Protons
Used to represent objects or ideas that are difficult to visualize or to picture in your mind
Models
Atoms of the same element that have different numbers of neutrons
Isotopes
Horizontal rows of elements in the periodic table
Periods
Area around the nucleus of an atom where electrons are most likely found
Electron cloud
Neutrally charged particles; no charge
Neutrons
the weighted average mass of all naturally occurring isotopes of an element, measured in atomic mass units (amu)
Average atomic mass
Uses the chemical symbol of an element surrounded by dots to represent the number of electrons in the outermost energy level
Electron dot diagram
Vertical columns in the periodic table
Groups
Protons and neutrons are made of smaller particles called
Calculate the number of neutrons in Carbon-12
6
These 2 elements are the building blocks of all other elements
Hydrogen and helium
In the 1800s this English scientist presented evidence to support the existence of models
John Dalton