The Basics of Atomic Structure

Terms you should know…

• Atom: smallest unit of an element that maintains the identity of that element.

• Chemical Reaction: Reaction where atoms combine in such a way to form new substances.

Atomic Structure

• Each element has a unique chemical identity. - The key to understanding the identity of an

atom is in it’s structure and the components that make up it’s structure.

Atomic Particle Distribution

Subatomic Particles Electron (e-)

(-) charge 1/1840 amu located outside the nucleus

Proton (p+)

(+) charge 1 amu Located inside the nucleus

Neutron (n0)

No charge 1 amu Located inside the nucleus

What’s amu?

• amu is shorthand for “Atomic Mass Unit (u)”Atomic Mass Units are the units used to express

atomic and molecular units.

One atomic mass unit (u) is roughly equal to the mass of one proton or one neutron.

In grams, one atomic mass unit (u) is equal to: 1.66053886 × 10−24 g

Nucleus

• In the center of the atom and contains the protons and neutrons

• Makes up 99% of the mass of the atom.

Elements in the Periodic Table• Atomic Number:This is the number of protons• In a neutral atom:Number of protons = Number of

electrons• Mass Number: Protons + Neutrons (total number of

particles in the nucleus)• Atomic mass: the average mass of all known

isotopes of the element– Most abundant isotope can be

found by rounding atomic mass to nearest whole number

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CCarbon12.001

So what’s your (atomic) number?• An element will always have the same number of protons regardless of the

number of neutrons and electrons. An element can be identified by its Atomic Number.

• IsotopesIsotopes are atoms of the same element with different number of neutrons. The mass number of isotopes of the same element are also different because the mass number is equal to neutrons + protons.

• All atoms of an element are considered an isotope, some are more common than others.

• An An IonIon is an element with a number of electrons thatelectrons that differ from its number of protons. An ion is a charged atom.– Cation is a positive ion– Anion is an negative ion

Notice: it’s the number of electrons and neutrons that change, not the atomic number!

Introduction to Isotopes• All atoms of an element are considered an isotopeAll atoms of an element are considered an isotope, only some

are more common than others. • Even though isotopes have different amounts of neutrons

they are still chemically alike since they have the same number of protons and electrons.

• Atomic massAtomic mass is the average of all isotopesaverage of all isotopes of the element.• To find the most common isotope round the atomic mass to

nearest whole number.-Ex: Carbon-12 is the most common isotope of carbon

Which isotope is the most common for the element Boron?Which isotope is the most common for the element Boron?

Isotope Notation

• Mass number is written to the top left.

• Atomic number is written at the bottom left.

What would the notation look like for Carbon 14?

So what are isotopes good for?

• Dope testing - one of the initial tests to determine if

someone has been doping with synthetic testosterone is a test for a high concentration of an isotope that’s not contained within naturally produced testosterone, but within the synthetic testosterone derived from yams.

More tests will have to be conducted if it is revealed that the athlete is a vegetarian with an affinity for yams.

Radiometric Dating

Making Bombs