Atomic Number and Mass Number Chapter 4 The Atom Atomic Number and Mass Number Isotopes

LecturePLUS Timberlake

LecturePLUS Timberlake Thomson

LecturePLUS Timberlake Rutherford

LecturePLUS Timberlake Bohr

Quantum Model/Wave Model/ Current Model LecturePLUS Timberlake Quantum Model/Wave Model/ Current Model

Subatomic Particles Particle Symbol Charge Relative Mass Proton p+ +1 1amu Neutron n 0 1amu Electron e- -1 0 amu Atomic Mass Unit (AMU) 1 AMU = 1/12 the mass of Carbon-12 atom (approx. 1.66 x 10 -27 kg)

Width of the nucleus 10-13cm Width of an atom 10-8 cm

I. Atomic Structure Atomic Number: Number of protons in an atom Atomic number identifies the type of element Example: Iron - ________ - _______ Atomic # 26 (26 protons)

All atoms of an element have the same number of protons 11 Na 26.1 Atomic # 11 protons Symbol Sodium Atomic mass

Learning Check 1 State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons

LecturePLUS Timberlake Atomic Charge: (Charge of the whole atom) The total charge of an atom is is ALWAYS neutral/0 What is the charge of a sodium atom? Example: Cobalt (Co) - __27 p______ and _27 e- Atomic # also equals number of electrons in an ATOM Number of protons = number of electrons in an ATOM

LecturePLUS Timberlake Learning Check 2 If a Magnesium atom has 12 protons how many electrons does it have? An Aluminum atom has 13 protons, how many electrons does it have?

Mass Number: # of protons + # of neutrons Example: Helium has 2 protons and 2 neutrons so the mass number is 4 Beryllium has 4 protons and 5 neutrons what is the mass number?

Calculating Parts of an atom LecturePLUS Timberlake Calculating Parts of an atom Look at Bromine on the periodic table. How many protons? 35 from atomic # How many electrons How many neutrons? Mass – atomic number 79.90- 35 = 44.9 – round to nearest whole # 45 neutrons

LecturePLUS Timberlake Parts of an atom How many protons, neutrons, and electrons in Iron?

II. Isotopes An isotope is a different version of the same element. Apples come in different varieties- golden delicious, granny smith, gala, etc. These varieties have different sizes and colors. Atoms are the same, the varieties of an atom are isotopes. An isotope is a different version of the same element. Isotopes are atoms of the same element (same # of protons) that have different numbers of neutrons and therefore different mass.

III. Isotopes Isotopic Notation: Shows the mass of an atom along with element symbol Mass # 4 5 Example: 94 Be ______ p; _______ n; _______ e- 4 Atomic # Example: C – 14 - ____ p: ____ n; ____ e 6 8 6 Mass #

II. Isotopes 1 1 11H 1 2 21H 1 1 2 3 31H

III. Isotopes Atomic # = 34 Mass # = 79 7934 Se Example: Find the number of neutrons in an atom of Se-79 Atomic # = 34 Mass # = 79 7934 Se # of n = Mass # - Atomic # = 79 – 34 = 45 n Example: Find the number of neutrons in an atom of Se-80 Atomic # = 34 Mass # = 80 8034 Se # of n = Mass # - Atomic # = 80 – 34 = 46 n

Learning Check 7 6 6 6 #P _______ _______ _______ Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______

Solution 7 6 6 6 #P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___ 12C 13C 14C 6 6 6 #P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___ #E __6___ _ 6___ ___6___

Learning Check 4 An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is C. The element is 1) Si 2) Ca 3) Se An atom has 10 protons and 10 neutrons. Its atomic number is Its mass number is The element is

IV. Calculating Atomic Mass The mass found on your period table is NOT the mass of a single atom of that element. That number is the atomic mass which is the average of the isotopes and their abundance for that element. (ex. – C’s atomic mass is 12.011) Atomic Mass: the average mass of the naturally occurring isotopes based on each of the isotopes’ abundance and mass number

IV. Atomic Masses How to find the atomic mass: Carbon has two naturally occurring stable isotopes . Most carbon atoms - 98.89% are C-12, while the remaining 1.108% are C-13. What is the atomic mass of carbon? (Count sig. figs. ONLY for percents! Then add and round to the place with least number of sig. figs) Divide by 100 Step 1: Convert % to decimal # and multiply the decimal by its mass number (0.9889) (12 amu) = 11.87 amu (0.01108) (13 amu) = 0.1440 amu Step 2: Add the masses of isotopes 11.87 amu + 0.1440 amu = 12.01 amu

IV. Atomic Masses 92.21% of Si is found to be 27.98 amu, 4.70% is found to be 28.98 amu, and the remaining 3.09% is found to be 29.97. Calculated the atomic mass of carbon 27.98 amu (0.9221) = 25.80 amu 28.98 amu (0.0470) = 1.36 amu 29.97 amu (0.0309) = 0.926 amu 25.80 amu + 1.36 amu + 0.926 amu = 28.09 amu

Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3

IV. Ions An atom that has gained or lost one or more electrons. # of protons does not equal # of electrons Example 23 11 Na 1+ Atomic # # of protons Mass # # of neutrons Ion Charge # of electrons

LecturePLUS Timberlake IV. Ions Anion: An atom that has gained electron(s). Negatively charged (two n’s for negative) Cation: An atom that has lost electron(s). Positively charged

LecturePLUS Timberlake Examples 7Li 1+ ____p ____n ____e _________ 31P 3- ____p ____n ____e _________ 79Se 2- ____p ____n ____e _________ 19F 1- ____p ____n ____e _________