Matter Quiz Atomic Theory Notes

Warm - Up Place your electronic device in Mr. Klotz’s bin when you come into class. Make sure your device is on silent If I have silver jewelry is it a homogeneous or heterogeneous? What about air? Any last minute questions?

Objective Today I will be able to: Demonstrate knowledge of matter and energy by taking a quiz Identify the parts of the atom and their isotopes Calculate atomic masses of isotopes given a set of data

Homework Atomic Structure Practice

Agenda Warm – Up Matter Quiz Atomic Theory Notes Atomic Theory Practice Exit Ticket

Atomic Theory Notes

Modern Atomic Theory Atom – smallest part of matter that represents a particular element Composed of electrons, protons, and neutrons Protons and neutrons (nucleons) form the nucleus of an atom Mostly empty space

Subatomic Particles Name Symbol Charge Proton p+ +1 Neutron n Electron Electron e- -1

9.109 x 10-28 (considered to be zero) Subatomic Particles Name Mass (g) Mass (amu) Location Proton 1.673 x 10-24 1 Nucleus Neutron Electron 9.109 x 10-28 (considered to be zero) .0005 Outside Nucleus

What information can we get from the periodic table?

Atomic Number number of protons in the nucleus You cannot change the number of protons!!! Determines the identity of an element Also the number of electrons in a neutral atom

Atomic Number What is the atomic number of carbon? 6 How many protons and electrons would there be in a neutral atom of carbon? 6 protons and 6 neutrons How many protons and neutrons would there be in a neutral atom of oxygen? 8 protons and 8 neutrons

Atomic Mass Measured in atomic mass units The number or protons and neutrons in an atom

How did we arrive at measuring atomic mass in atomic mass units? Based on the Carbon-12 scale By international agreement, a carbon atom contains 6 protons and 6 neutrons, or 12 amu Therefore, 1 amu is 1/12 of a carbon atom Since the mass in grams of protons and neutrons are about the same, they both have an atomic mass unit of 1

Why aren’t electrons accounted for in the calculation of the atomic mass? Electrons are small! It takes almost 2,000 electrons to equal the mass of one proton or neutron Electrons are assumed to have a mass of 0 amu

If each proton and neutron has a mass of one amu, then why aren’t the atomic masses on the periodic table whole numbers? Isotopes of elements atoms with the same number of protons but different numbers of neutrons

Isotopes Some isotopes are found more common than others We can determine which isotope is more common by looking at the atomic mass Atomic Mass is calculated weighted averages

How do we calculate a weighted average? Category Score Exams (50%) 80% Labs (25 %) 75% Classwork (15 %) 95% STEM fair (10 %) 87% (.50 x 80) + (.25 x 75) + (.15 x 95) + (.10 x 87) = 81. 7 % = 82 %

Atomic Mass is calculated using the same method of weighted averages Carbon Isotope C – 14 1% C - 12 99% (.01 x 14) + (.99 x 12) = 12.02 amu

Ions When an atom gains or loses an electron, an Ion is formed Cation – atom loses an electron and makes a positive ion Example: Lithium (Li) loses one electron It becomes Li+ Anion – atom gains an e- and makes a negative ion Example: Sulfer (S) gains two electrons It becomes S-2

Ions Examples What is the chemical symbol for the ion with: 13 protons and 10 electrons - Al+3 7 protons and 10 electrons - N-3

How many protons and electrons are present in a(n): S-2 ion - 16 p+ and 18 e- Li+1 ion - 3 p+ and 2 e-

Be careful with terminology! Atomic Mass – average mass of the naturally occurring isotopes of an element Seen on the periodic table Mass Number – number of protons and neutrons in an atom’s nucleus Seen in symbolic representations

Symbolic Representations of Elements An atom with 7 protons and 7 neutrons has a mass number of 14 and is usually written as… N 14 7

Al+3 Se-2 How many protons, neutrons, and electrons? 27 Al+3 13 13 p+, 14 n, and 10 e- 79 Se-2 34 34 p+, 45 n, and 36 e-

Exit Ticket Draw the symbolic representation of the K1+ ion