The Nuclear AtomAtoms differ from one another by their number

of:1. Protons

2. Neutrons

3. Electrons

Electrons have a NEGATIVE charge. The MASS of an electron is 1/1840 less massive than either a proton or a neutron.

The ELECTRONS in an atom are responsible for the chemical properties

of the element.

The Nuclear Atom

The nucleus contains PROTONS and NEUTRONS.

Protons and neutrons have the same mass1.66 x 10-24 g (actual)

1 (relative)

Protons are POSITIVENeutrons are NEUTRAL

The Nuclear AtomIn a NEUTRAL atom, the number of protons =

number of electrons.

Determine the number of electron in a neutral atom that has 13 protons.

13

The Nuclear AtomThe identity of an atom is determined by the

number of PROTONS.

The number of PROTONS in an element is represented by the ATOMIC NUMBER

The numbers of NEUTRONS and PROTONS in an element are represented by the MASS

NUMBERThe PROTONS and NEUTRONS make up the mass of an atom and are responsible for the

stability of the atom.

What is an isotope?

• An isotope is an atom with the same number of protons, but different numbers of neutrons.

• Every atom is considered an isotope.

The Nuclear Atom

Standard Nuclear Notation is used to represent each isotope in existence.

XAZ

X = element symbolA = Mass Number

Z = Atomic Number

The Nuclear AtomExample 1:

Write the symbol for the atom that has an atomic number of 9 and a mass number of 19.

F199

How many protons, neutrons and electrons does this atom have?

PROTONS = 9NEUTRONS = 10ELECTRONS = 9

The Nuclear AtomThe atomic masses of elements are calculated from

EVERY STABLE ISOTOPE of the element.

Calculating the AVERAGE ATOMIC MASS:

Atomic Mass Unit- Defined as 1/12 the mass of ONE atom of CARBON – 12 (1.66 x 10-24 g).

The mass of each element is a weighted average of the isotopes of the element.

Isotope Example• Calculate the following:

– Jodi scored the following grades:Homework: 100,70,100Quizzes: 98,88,72Tests: 62

What is Jodi’s average?

Isotope Example• Calculate the following:

– Jodi scored the following grades:Homework: 100,70,100Quizzes: 98,88,72Tests: 62

What is Jodi’s average if homework counts 20%, quizzes count 30% and tests count 50%?

Isotope Example

# Muffins Mass(g) % Abundance

Mass contribution

2 25.6

1 27.9

3 25.2

• Calculate the following:

– Khori has 6 blueberry muffins. The muffins have the following masses:

The Nuclear AtomExample 1:

Silicon has three stable isotopes. The following information is available for the three isotopes:

Isotope Mass (amu) Fractional Abundance

(%)Silicon – 28 27.977 92.21Silicon – 29 28.976 4.70Silicon – 30 29.974 3.09

(27.977 amu · 0.9221) + (28.976 amu · 0.0470) + (29.974 amu · 0.0309)

= 28.09 amu

The Nuclear AtomExample 1:

Iron has four stable isotopes. The following information is available for the four isotopes:

Isotope Mass (amu) Fractional Abundance

(%)Iron – 54 53.9396127 5.845 Iron – 56 55.9349393 91.754 Iron - 57 56.9353958 2.119 Iron - 58 57.9332773 0.282

= 55.85 amu