Transcript Protons PP

Protons & Valence Electrons
8.5B: Identify that protons determine an element’s identity,
valence electrons determine its chemical properties,
including reactivity
Protons
Protons are positively-charged, subatomic particles
found in the nucleus of an atom. They contribute to
the mass of an atom. They ARE the IDENTITY of the
atom. The number of protons does not change.
The atomic number IS
the number of protons
An atom with 8 protons
is ALWAYS Oxygen
Protons are the Identity of Atoms
Each element has a unique number of protons in all of its atoms.
The atomic number of an element is the number of protons in
each of its atoms. To identify which element a model of an atom
is depicting, count the number of protons in the nucleus and find
the element on the periodic table with that number. Can you
identify these atoms?
Valence Electrons
Valence electrons are the electrons in the outermost
energy level or orbital. They determine an atom’s
reactivity.
This Carbon atom has
four valence
electrons.
Reactivity
Reactivity is the rate at which a chemical substance
tends to undergo a chemical reaction (bond with other
atoms)
Lithium reacting with water
Valence Electrons
In the Bohr Model of the atom, electrons fill
different electron energy levels from the inside out.
The first orbital can only hold two electrons. The
second orbital can hold eight electrons, and the third
can hold up to eighteen, but the outermost energy
level can never have more that eight electrons. Only
these outermost electrons, known as valence
electrons, can interact with other atoms in chemical
reactions.