atomic structure

atom

smallest part of matter that still retains properties of an element

Components of an atom

(subatomic particles)

• protons (positive charge)

• neutrons (no charge)

• electrons (negative charge)

atom’s properties

• protons and neutrons are in nucleus, electrons orbit outside

• can be inferred by location on periodic table (which relates to # of electrons in outermost shell)

• can gain, loose, or share electron‘s to make a variety of chemical bonds of varying strengths/properties

what determines the chemical properties of an element?

The # of electrons and protons.

number of protons in an atom

determines what kind of element it is

in a neutral state, the # of protons and electrons are equal.

Can an atom of 1 element have varying # of neutrons and electrons?

Yes!

If # of neutrons is different, it’s called an ISOTOPE

if # of electrons is different, it’s called an ION.

ion

when the # of protons and electrons in an atom are not the same

means it has a charge (±/-)

Ions

Cation- an atom that loses an electron (so it is positively charged)

Anion - an ion that gains an electron so it is negatively charged

atomic mass

the sum of the mass of protons and neutrons in one ato,

why is the atomic # not a whole #?

different types of the same element atom can vary in the # of neutrons

electron shells

• groups of electrons orbiting together

• can be multiple layers

• w/in shells, sub shells are labeled s, p, d, and f; s - closest to nucleus

valence electrons

• those in outermost electron shell

• can be shared with other atoms

• are in most stable state when valence shells are filled; usually 8 electrons

• the fewer valence electrons the more reactive they are (willing to bond with other atoms); but are stable

• noble gases (8 valence electrons), really stable, don’t react, complete valence shells - group 18

Periods (rows) in the Periodic Table

• refers to element’s # of electron shells

Groups in periodic table (vertical columns)

• refer to # and configuration of an element’s valence electrons

• elements in same group have similar chemical properties

• gives you an idea about how those elements bond

• there are 8 groups

Atomic #

The # of protons an atom has

Reading left to right on Periodic Table and starting with 1, each column(group)has an additional proton (so Carbon in row 14 has 14 protons)

How to Read Periodic Chart of Elements

• each box represents an element, abbreviated with 2 ltrs

• the # in the upper left corner tells you # of PROTONS in that element in the nucleus of the atom

• numbers in lower right corner is ATOMIC MASS

• COLORS OF BOXES indicate metal vs. non-metal

• upper left columns left to right: signifies # of protons, start w/1 and add one for each column

electron shell #’s

first shell - can hold 2 electrons

2nd shell - can hold 8 electrons

3rd shell - 18 electrons

4th shell - 32 electrons

number of elements

118 total

92 naturally occurring

rest made in labs

elements that make up most living organisms

carbon, hydrogen, oxygen, nitrogen

covalent bond

two atoms share electrons

ionic bond

an atom that needs electrons steals one from another atom to have a complete electron shell; it holds the atoms together through electro-static forces

isotope

• when the # of neutrons varies in an atom

• all isotopes of an element have the same # of protons and electrons