CHEMISTRYNovember 13, 2014

ISOTOPES

SCIENCE STARTER• Read the Science starter and

annotate the text. Make sure to indicate in your annotation where you found the answer to the question/prompt.• You have 7 minutes to complete the

Science Starter. • You are seated and silent

ANNOUNCEMENT

•MIDTERM – Next Friday

AIM/GUIDING QUESTION

• Give evidence to justify which isotope of oxygen can be found more in the glaciers of the polar region?

ISOTOPES• Isotopes are atoms of the same element

that have the same number of protons but different numbers of neutrons.–OR

• Isotopes are atoms of the same element that have the same atomic number but different mass numbers

REMEMBER

• The number of protons in the nucleus of an atom is the Atomic Number of that atom and defines which type of atom it is, that is - which element the atom is a particle of.

MASS NUMBER

• The number of neutrons in the nucleus of an atom is the Mass Number (or "Atomic Mass") of the atom - the Atomic number of the atom

ISOTOPE NOTATIONS

–Example: Carbon – 14 (Element name is carbon and mass number is 14)–Example: C-14 (Element symbol is C

(carbon) and mass number is 14)–Example: 14C (element symbol is C and

mass number is 14)–Example: (Element symbol is C, mass

number is 14 and atomic number is 6)

ATOMIC MASS

–The weighted average mass of all the naturally occurring isotopes of an element.–Need relative abundance and

atomic mass to calculate the weighted average mass or average atomic mass

CALCULATING ATOMIC MASS

Example: Carbon has two naturally occurring isotopes - 98.89% Carbon-12 and 1.108% Carbon-13Solution: Convert the percentages to decimals and multiply the mass of each isotope by the relative abundance and add together.

Percent x mass.9889 x 12 = 11.87.01108 x 13 = + 0.1440

Total: 12.01

ELECTRON WKSHT (4)

• Electron Configuration represents the distribution of all electrons for an element. – The electron configuration shown on the periodic

table is at ground state.• Adding the number shown in the electron

configuration will give the number of electrons for an element. Example: 2-7-2 = 11 electrons