Chemistry 1 Unit 1 Full Notes, Lecture notes of Chemistry

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U N I T 1 A T O M I C S T R U C T U R E

W H AT I S C H E M I S T RY?

WHAT IS CHEMISTRY?

• Let’s start with a definition of CHEMISTRY
• The study of substances (elements, compounds, & mixtures) composition & structure and their interactions.
• What does this mean? Let’s unpack this. Always good to break down terms and concepts.
• Elements “your understanding?”
• Compounds
• Mixtures

COMPOUNDS

• Compounds
• Definition
• Two or more elements chemically bonded
• We can see this in chemical formulas: CO 2 H 2 O CH 3 COOH NaCl NaOH
• Chemical formulas gives the number and kind of elements in a compound.
• Compounds are Pure Substances
• Examples: https://www.youtube.com/watch?v=NTFBXJ3Zd_ Na (s) + Cl 2 (g) 
• demonstration: Mg(s) + O 2 (g)  2MgO(s)
• The compound has different properties than its individual make up

MIXTURES

• Definition
• A blend of 2 or more pure substances NOT chemically combined
• Each substance retains its own properties
• Example: Salt and Pepper Sand and rocks Italian salad dressing
• Gatorade: water sugar electrolytes dye
• Types of Mixtures.
• Heterogeneous Mixture
• Concentration of particles are NOT evenly spread throughout.
• Cookies, concrete, salad dressing
• Not dealt with very often in chemistry

COMPOSITION & STRUCTURE

• What is meant by the composition of an element/atom, or a compound or a mixture?
• Composition is what the substance is made of
• What is the composition of an atom?
• Protons, neutrons, & electrons.
• Structure is how these particles are arranged.
• How are the protons, neutrons and electrons arranged in an atom?
• How about a compound like Ethanol?
• Chemical formula is: C 2 H 5 OH What is its composition?
• 2 -carbon atoms 5- hydrogen atoms 1- hydroxide
• Practice: Ca 2 (PO 4 ) 3 or C 3 H (^8)

COMPOSITION & STRUCTURE

• Structure is how these particles are arranged.
• What is the structure of ethanol?
• Why is the structure of a substance so important?
• The structure denotes its function.
• Alcohol substances are flammable. How do we identify an alcohol?
• Hydrocarbon + OH
• Why does sodium react differently in water than aluminum. Both are gray metals.
• https://www.youtube.com/watch?v=NTFBXJ3Zd_
• https://www.youtube.com/watch?v=CEC64Bqeajs

STRUCTURE OF AN ATOM

• SAP: subatomic particles (3) comparison.
• Protons, neutrons, electrons
• Proton: mass 1.673x10-24^ g = 1 amu
• Charge = +1.602x10-19^ C (coulomb)
• Found in the nucleus
• Neutron: mass 1.673x10-24^ g = 1 amu
• No charge
• Found in the nucleus
• Electron: mass 1/~2000 of a proton 9.11x10-28^ g
• Charge: - 1.602x10-19^ C
• Found outside of the nucleus
• ** neutral atom means????

VOCABULARY AND APPLICATION

• Atomic Number
• 1. Gives number of protons in an atom
• 2. • Identifies an element
• 3. Found on the periodic table
• Atomic Mass- weighted average of isotopes…decimal (on periodic table)
• Mass number
• 1)Number of protons and neutrons in an atom
• 2)Not found on the periodic table…..whole number
• 3. If information is not available for mass number, we will round the atomic mass to nearest whole number and consider this the mass number: Al? P?

WRITING COMPLETE CHEMICAL SYMBOLS OF ELEMENTS

• Draw the symbol of an element: Carbon
• On the bottom left of the symbol, write the atomic number (Z)
• 6 𝐶𝐶
• On the top-left side, write the mass number
• 126 𝐶𝐶
• IF we don’t know the mass number, round the atomic mass to nearest whole number.
• Practice: writing the symbols for the following elements: Aluminum, Selenium, Copper, Calcium, Bromine, Molybdenum, Strontium, Lead

IDENTIF Y THE # OF PROTONS, ELECTRONS, NEUTRONS IN AN ELEMENT

• Using the Carbon symbol, identify the # of protons, electrons and neutrons. *remember, atoms are neutral.
• 126 𝐶𝐶
• Do the same for Aluminum, Selenium, Copper, Calcium, Bromine, Molybdenum, Strontium, Lead
• Write the symbol for an atom with 14 protons, 14 neutrons, and 14 electrons
• 1428 𝑆𝑆𝑆𝑆
• Write the symbol for an atom with 73 neutrons, 51 electrons and 51 protons.
• 12451 𝑆𝑆𝑆𝑆
• Homework

ANIONS

• Non-metals are located to the right of the staircase on the periodic table
• These ions have a name change. Change the ending to “ide”
• Oxygen (O 2 is a molecule) as an ion O2-^ name is Oxide.
• Nitrogen  nitride N 3-^ Phosphorus  phosphide P3-^ Sulfur  sulfide S2- fluorine  fluoride F1-
• Symbol: 168 𝑂𝑂2-
• Charge is written as the number first and then the sign: 2 -^2 +^ NOT -2 +
• How many protons? Neutrons? Electrons?

ANIONS

• Elements can lose electrons to become ions
• Metals tend to lose electrons
• Metals are on the left side of the staircase
• When an atom loses electrons, the ion becomes a Positive ion
• No name change
• Called a CATION.
• Example: 1327 𝐴𝐴𝐴𝐴3+
• How many protons? Neutrons? Electrons?
• Write the complete chemical symbol for the substance that has 50 protons, 70 neutrons and 46 electrons
• Write the complete chemical symbol for the substance that contains 16 neutrons, 15 protons and 18 electrons.

ISOTOPES

• To do so we need two data: mass of each isotopic atom and percent abundance of each isotope.
• Carbon – 12 has a mass of 12.000 amu and a percent abundance of 98.89%
• Carbon – 13 has a mass of 13.003 amu and a percent of 1.11%
• This data is used to calculate a weighted average of the masses of the isotopes.
• Calculate Carbon’s Atomic Mass.
• Atomic Mass is an element’s weighted average of all of its isotopes.

ISOTOPES

• Calculate the same way we calculate your grades
• T 1 [84.5]= 80%, E 1 [91.6] = 20%
• Final = (.80 x 84.5) + (.20 x 91.6)
• Final = 85.
• For weighted averages we DO NOT divide.
• Atomic Mass = (.9889 x 12.000amu) + ( .0111 x 13.003amu)
• Atomic mass of Carbon = 12.01amu