Basic Chemistry Review for test

What is an atom?

Answer: The basic unit of all matter Small in size

What are the subatomic particles in an atom?

Answer Proton Neutron Electron

Where are the 3 subatomic particles found?

Answer Proton and Neutron – NUCLEUS of the atom (center) Electrons – found rapidly moving in energy levels (energy clouds)

What are the electrical charges to the subatomic particles?

Answer Proton = Positive (+) Neutron = Neutral (0) Electron = Negative (e-)

What subatomic particles contribute to the MASS of the atom ?

Answer Proton Neutron Remember – the electrons are SOOOO LIGHT that they are not part of the mass (atomic weight)

How are atoms considered “electrically equal” or “neutral”?

Answer There is an equal number of protons and electrons If there are more protons – then the atom would have an overall POSITIVE charge If there are more electrons – then the atom would have an overall NEGATIVE charge

Label the following: Use the terms Symbol Atomic Weight (Mass) Atomic Number

Answer A Atomic Number Symbol Atomic Weight (mass)

What are the main elements found in living things?

Answer Hydrogen Oxygen Nitrogen Carbon There is also phosphorus and sulfur, but I only want you to focus on the four listed above.

Practice The symbol for Krypton is The mass number for Calcium is The atomic number for Beryllium is

Practice The symbol for Krypton is Kr The mass number for Calcium is The atomic number for Beryllium is 4

What does the coefficient represent?

Answer The number of molecules present LARGE NUMBER written before the element symbol Ex: 4CO2 There are 4 molecules of carbon dioxide

What does the subscript represent?

Answer The number of atoms present SMALL NUMBER written within the chemical formula Ex: 4CO2 There are 8 atoms of oxygen Remember to distribute (4 x 2=8)

More Practice 5C2H4 How many molecules are present? How many atoms of Carbon are present? How many atoms of Hydrogen are present? How many TOTAL atoms are present?

More Practice - Answers 5C2H4 How many molecules are present? 5 How many atoms of Carbon are present? 10 (5x2 – remember to distribute) How many atoms of Hydrogen are present? 20 (5x4 – remember to distribute) How many TOTAL atoms are present? 30 (distribute and then add up) (5x2) = 10 (5x4) = 20 10 + 20 = 30

Chemical bonds involve … A. Electrons B. Protons C. Neutrons D. Valence Electrons

ANSWER = Chemical bonds involve … A. Electrons B. Protons C. Neutrons D. Valence Electrons Choice D is the most accurate answer here

In covalent bonds, electrons are … Gained Lost Shared

ANSWER - In covalent bonds, electrons are … Gained Lost Shared

Where are valence electrons found?

Answer In the outermost energy level of an atom

How many electrons should be in the valence shell to have an atom be considered “Stable and Unreactive”

Answer 8 electrons!

What rule does this 8 number follow?

Answer 8 – OCTET rule ****EXCEPTION**** The outermost energy level will be complete when it contains 8 electrons. Atoms will gain/lose/share electrons to reach this stability! ****EXCEPTION**** Hydrogen and Helium follow the DUET RULE (can only have 2 electrons in the outermost shell to be stable and unreactive)

Which of the following atoms are unstable and reactive? Carbon Neon Helium Magnesium

ANSWER - Which of the following atoms are unstable and reactive? Carbon – 4 opportunities to bond (vacancies) Neon Helium Magnesium – 6 opportunities to bond (vancancies) Neon is stable because it is a noble gas – already has 8 electrons Helium is stable because it is also a noble gas – but follows duet rule so it has 2 electrons

What’s the difference between a… Single Bond Double Bond Triple Bond

What’s the difference between a… Single Bond Atoms share 2 electrons (1 pair) Double Bond Atoms share 4 electrons (2 pairs) Triple Bond Atoms share 6 electrons (3 pairs)

What does a structural formula tell us?

Answer - Types of Elements Number of atoms Location of atoms Example – 1 Oxygen 2 Hydrogen

What do the lines represent in a structural formula ?

Answer COVALENT BONDS SHARING OF ATOMS!!

Draw the Lewis Dot Structure of Phosphorus Hydrogen Nitrogen Oxygen

ANSWER Draw the Lewis Dot Structure of Phosphorus Hydrogen Nitrogen Oxygen

This is the bohr model for what compound?

Answer WATER

What is the structural formula for C2H6

Answer

What is a chemical reaction?

Answer Changes or transforms one set of chemicals into another CHANGES to the BONDS – breaking and reforming bonds

What’s the difference between… Reactants Products

ANSWER What’s the difference between… Reactants ENTER into a chemical reaction (before the arrow) Products PRODUCED by a chemical reaction (after the arrow)

Label the diagram using the following terms… Reactants Products Coefficients Subscripts

ANSWER Label the diagram using the following terms… C - Reactants D - Products A - Coefficients B – Subscripts Reactants REACTto produce PRODUCTS

What is the Law of Conservation of Matter?

Answer Matter cannot be created nor destroyed Arrangement of atoms is what is changed # each atom in Reactants must equal # each atom in products The mass of reactants = the mass of products

Is this equation balanced? Na + Cl2  NaCl

Is this equation balanced? ANSWER - NO 2Na + Cl2  2NaCl

What are the properties of water ?

Water is polar It has polar covalent bonds between the atoms It has hydrogen bonds between the molecules (weaker than covalent) Cohesion, adhesion, liquid is more dense than the solid, high heat capacity, universal solvent