Download Atoms Notes Powerpoint 2020

ATOMS:
WHAT THE WORLD IS MADE OF!
ELEMENTS
• Element – a substance made of only ONE
kind of an atom
– Cannot be broken down into simpler
substances
– Represented on the Periodic Table of
Elements
Example:
ATOMS
• Smallest particle of an element that still
retains the properties of that element
• Mostly open space!
• Made up of a central Nucleus orbited by
one or more electrons
• Too small to be seen. Models are used to
study the atom
– Bohr model (planetary model)
– Electron cloud model
– Lewis Structure diagram
BOHR MODEL OF SODIUM
ELECTRON CLOUD MODEL
LEWIS STRUCTURE
(a.k.a. Electron Dot Diagram)
These models only show
the valence electrons –
the electrons on the
outer most shell of an
atom.
(Example: Sodium, Na, has 11 electrons total but
only 1 valence electron)
Valence electrons are
involved in chemical
bonds & reactions
between atoms.
STRUCTURE OF THE ATOM
• Nucleus – tiny central core of the atom
Subatomic particles found inside the nucleus –
– 1) Protons – have a positive (+) charge
– 2) Neutrons – have no charge (0) neutral
• Electron Cloud – area outside of the
nucleus
– (aka “shells” or “energy levels”)
Subatomic particles outside the nucleus:
3) Electrons – have a negative
(-) charge and orbit rapidly
around the nucleus
Subatomic Particles
• Sub = “smaller than”
• Subatomic particles are particles that are
smaller than an atom
• Protons, Neutrons and Electrons are all
examples of subatomic particles
ATOMIC CHARGES
• Atoms are normally electrically neutral (0).
WHY?
– For every positive (+) charge, there is a
negative (-) charge.
In other words:
Equal number of protons (+) and electrons(-)
gives the atom an overall neutral (0) charge.
MORE ABOUT ELECTRONS!!
• Electrons move rapidly around the
nucleus.
• Smallest of the sub-atomic particles
– Too small to count towards an atom’s mass!
• Electrons move so fast
that they look like moving
fan blades!
It’s Electric!
• Electrons near the nucleus are held tight
to the atom (opposites attract!)
• Electrons further out are not & can be
made to move out of their orbits.
• Moving electrons create electricity!
ATOMIC NUMBER
• Atomic number Identifies an element.
• Equal to the number of protons an
element has.
• EX: Every atom of carbon has 6 protons
– Therefore, carbon’s atomic number is 6
Every atom of oxygen has 8 protons
What is oxygen’s atomic number? ___
All atoms of the same element have the same
chemical properties and the same number of
protons. If the number of protons changes, then
you have a DIFFERENT element.
ATOMIC MASS
• Most of an atom’s mass is in the nucleus
(where the protons and neutrons are)
• AMU – Atomic Mass Unit – used to measure
the mass of an atom
– Mass of a proton or neutron = 1 amu
– Mass of an electron = about 0.0005 amu
• It takes almost 2,000 electrons to = 1 amu!
• Electrons are generally ignored when calculating an
atom’s mass because they are so tiny
• Atomic Mass = Protons + Neutrons
Mass & Volume
• Most of an atom’s mass comes from the
protons (+) and neutrons (0) in the
nucleus.
• Most of an atom’s volume comes from the
space where the electrons move.
ISOTOPES
• Atoms of an element always have the same
number of protons, but the number of
neutrons can be different.
• This is called an isotope of an element
– Isotopes: atoms of the same element with different numbers of
neutrons than average
• EXAMPLE: Carbon always has 6 protons, but
it could have 5, 6, or 7 neutrons.
– (Known as isotopes C-5, C-6, or C-7).
• Question: How many electrons would an
isotope of carbon have?
Common Isotopes of Carbon:
VALENCE ELECTRONS
• Farthest away from the nucleus
– on the outer most shell
– Not held as tightly by the atom
• Determine the properties and reactivity
of the atom.
• Form the chemical bonds between atoms
– Chemical bonds are the force that holds the
atoms together in a compound (atomic glue)
Next time…..
The Periodic Table of Elements!!!