7th Grade Science Final Review

(a) How many electrons does an F atom have? (b) If Fluorine is represented as F1-, now, how many electrons does it have

(a) 9, (b) 10

In ionic compounds, the sum of the charges of all the positive ions and the negative ions must be

0

How many moles of salt are required to make 2 liters of a 0.3 Molar solution?

0.6 Moles

How might you separate a mixture of sand and salt?

1. Heat the mixture until one of the components melts and then filter the one that did not melt, 2. Just add water and then filter followed by evaporation

Classify the following changes as physical or chemical: 1. Wood burns to ashes, 2. Water begins to Boil, 3. Grass Grows, 4. A Rock is crushed to powder

1. chemical, 2. physical, 3. chemical, 4. physical

The higher elements like Lead (Pb) #82, require an extra number of neutrons to hold the nucleus together. The mass number of Lead is 207. How may neutrons does Pb have?

125 neutrons

Compared to the MASS of a hydrogen atom, the MASS of an oxygen atom is

16 times greater

How many PROTONS should be added to the nuclei of oxygen atoms so the resulting gas will glow red when an electric current flows through it?

2

Zinc Phosphide, Zn3P2, is often used as a rat poison. Phosphorus has 5 valence electrons. How many valence electrons does each zinc atom lose?

2

How many electrons does the Calcium atom tend to lose?

2 Electrons

The first shell of an atom can hold a maximum of

2 electrons

How many nonbonding pairs are there in the valence shell of an Oxygen atom? How many unpaired valence electrons?

2 nonbonding pairs, 2 unpaired electrons

Na atom has 11 electrons. The electron configuration for Na is

2,8,1

What is the electron configuration for Mg?

2,8,2

Suppose an Oxygen atom gains two electrons to become an Oxygen ion. What is its electric charge?

2-

Write a correctly balanced synthesis equation.

2H2 + O2 --> 2H2O

Balance the equation for the production of NaBr from Sodium and Bromine.

2Na + Br2 ----> 2NaBr

What is the correctly balanced chemical equation that accurately represents what happens when Sulfur and Oxygen react to from Sulfur trioxide.

2S + 3O2 ----> 2SO3

How many shells are completely filled in an Argon atom?

3 Shells

How many covalent bonds are there in one molecule of silica, SiO2?

4 Covalent Bonds

How many electrons are shared in a double covalent bond?

4 electrons

How many grams of sodium chloride are needed to make 15 L of a solution that has a concentration of 3.0 g per liter of solution?

45 grams

When Iron metal reacts with Oxygen, the reaction can from (iron oxide) Fe2O3. What is the chemically balanced equation for this?

4Fe + 3O2 ----> 2Fe2O3

Boron atom has 5 protons. Its number of electrons is

5

How many grams of sucrose are there in 3 liters of a sucrose solution in water that has a concentration of 2 grams of sucrose per liter of solution?

6 grams

Describe how electrons are transferred in an ionic bond.

A metal atom loses electrons an da nonmetal atom gains electrons.

Which has more atoms: a 1-gram sample of carbon-12 or a 1-gram sample of carbon-13?

A one gram sample of carbon-12

A user is constructing an ionic bond between Beryllium and Chlorine and has reached the stage where Beryllium has 1 valence electron and chlorine has 8 valence electrons. What should the user do next?

Add another Chlorine atom, OR transfer an electron from the beryllium atom to the chlorine atom

Balance the equation for the production of AgCl + NaNO3 from AgNO3 + NaCl

AgNO3 + NaCl ----> AgCl + NaNO3

What is a valence electron?

An electron of the outermost occupied shell of an atom

What is the difference between an element and a chemical compound?

An element consists of only one type of atom

Unknown element X has four shells, five valence electrons, and is a metalloid. What is element X?

As

Why are atoms invisible to visible light?

Atoms are smaller than the wavelength of visible light

What is the chemical formula for the ionic compound Barium Nitride?

Ba3N2

The formula for the compound Beryllium Chloride is

BeCl2

The halogen that is a liquid at room temperature is

Br

Methan, CH4, burns in Oxygen gas to from Water and Carbon Dioxide. What is the correctly balanced chemical equation for this reaction.

CH4 + 2O2 ----> 2H2O + CO2

If two protons and two neutrons are removed from the nucleus of an Oxygen atom, a nucleus of which element remains?

Carbon-12

Many dry cereals are fortified with iron, which is added to the cereal in the form of small iron particles. How might these particles be separated from the cereal?

Collect the iron fillings with a magnet

Classify the following bonds as ionic, covalent, or metallic (O with F, Ca with Cl, Na with Na)

Covalent, Ionic, Metallic

Atoms of the same elements are alike (One atom of Oxygen is like another atom of Oxygen). Atoms of different elements are different (One atom of Oxygen is different from an atom of Nitrogen). This was proposed by

Dalton

The smallest piece of matter was named "atomos" or atom by

Democritus

Of the elements Cu, K, P, and F, which would you expect to have the greatest electronegativity?

F

Which combination of atoms can form a POLAR COVALENT BOND (H and H, H and Br, N and N, Na and Br)?

H and Br

Clean dry air is an example of a

Homogeneous OR Heterogeneous Mixture

Which of the following elements undergoes sublimation (Fluorine, Chlorine, Bromine, Iodine)?

Iodine

What type of chemical bond would you expect between a Cesium atom and a Bromine atom?

Ionic Bond

Why is ruby gemstone considered to be a solution?

It is a homogeneous mixture of chromium in aluminum oxide

Do metals more readily gain or lose electrons?

Lose electrons

What type of bonding might you expect between two Lithium atoms?

Metallic

What is the formula for the compound Magnesium Oxide?

MgO

List some properties of metals.

Most metals are ductile, malleable, and are good conductors of electric current

Which of the following formulas represents a compound whose molecules contain a triple bond? (O3, N2, Cl2, O2)

N2

Does Francium have the highest electronegativity on the periodic table?

NOPE

Hydrochloric acid, HCl, is addd to solid NaOH. After the reaction is complete, Sodium Chloride dissolved in water remains. What are the products of this chemical reaction?

NaCl & H2O

The most abundant element in the Earth's atmosphere is

Nitrogen

Oxygen atoms are used to make water molecules. Does this mean that oxygen, O2, and water, H2O, have similar properties? Why do we drown when we breathe in water despite all the oxygen atoms present in this material?

No, compounds are uniquely different from the elements from which they're made.

What type of chemical bond would you expect between two Bromine atoms?

Non-polar Covalent

What type of chemical bond would you expect between two Neon atoms (metallic, ionic, covalent)?

None of the above

Each night you measure your height just before going to bed. When you arise each morning, you measure your height again and consistently find that you are 1 inch taller than you were the night before but only as tall as you were 24 hours ago! Is what happens to your body in this instance best describe as a physical change or a chemical change?

Physical change because it readily reverses

"An atom is mostly empty space." Which scientist discovered this?

Rutherford

Which element below is a metalloid (Sb, C, Ga, Sn)?

Sb

If you eat metallic sodium or inhale chlorine gas, you stand a strong chance of dying. Let these two elements react with each other, however, and you can safely sprinkle the compound on your popcorn for better taste. What is going on?

Sodium Chloride (the compound) has nothing in common with its parent elements, sodium and chlorine

List some metals.

Sodium, Chromium, Copper

Rutherford's gold foil experiment provided evidence for what?

That there is a dense, positively charged mass in the center of an atom

What is the difference between a compound and a mixture?

The components of a mixture are not chemically bonded together

What do chicken noodle soup and garden soil have in common?

They are both examples of heterogeneous mixtures

How reactive are alkali metals?

They are so reactive that they are stored in oil

Who came up with the Plum Pudding model (also referred to as the Chocolate Chip model) of the atom?

Thomson

A solution that is capable of dissolving additional solute.

Unsaturated solution

Is F-As a very polar bond?

Yes, they are far away from each other on the periodic table

A Li atom has 3 protons, and 4 neutrons. What would be formed if one PROTON only is aded to this atom (remember, no change in the number of electrons since no electrons are being added)?

a Be ion

Mendeleev arranged the known chemical elements in a table according to increasing

atomic mass

The modern periodic table is arranged in order of increasing

atomic number

The Aluminum ore is called

bauxite

Na atom loses an electron to a G atom. Is this an example of a physical or chemical change?

chemical change involving the formation of positive ions of Na

Classify the following as element, compound, or mixture: table salt, stainless steel, table sugar, aluminum, ice (made from pure water).

compound, mixture, compound, element, compound

J. J. Thomson's experiments provided evidence that an atom

contains negatively charged particles

Name this compound: Li2O

diLithium monoxide

The proper name for the chemical compound N2O is

dinitrogen monoxide

A purifying process in which a vaporized substance is collected by exposing it to cooler temperatures over a receiving flask, which collects the condensed purified liquid.

distillation

If one NEUTRON is added to a helium nucleus, the result is

helium

Strontium, Sr (number 38), is especially dangerous to humans because it tends to accumulate in calcium-dependent bone marrow tissues (calcium, Ca, number 20). This fact relates to the organization of the periodic table in that strontium and calcium are both

in group 2 of the periodic table

Covalent and ionic bonds differ in that

ionic bonds don't involve the sharing of electrons

The alloy Bronze is not listed in the periodic table because

it is a mixture of different elements

When a solution is concentrated

large amounts of solute are dissolved in solvent

In Neils Bohr's model of the atom, electrons move

like planets orbiting the sun

The atoms of materials that conduct electricity best tend to be held together by

metallic bonds

Two isotopes of carbon are carbon-12 and carbon-14. These isotopes differ from one another by two

neutrons

When two different elements combine to form a compound resulting properties of the compounds are

not necessarily anything like those of the elements

The boiling temperature of water is so much higher than that of methane because water molecules are

polar

Protons are _____ charged and Electrons are _____ charged

positively, negatively

The atomic number of an atom is defined in terms of its number of

protons

Which is the smallest particle (neutron, atom, proton, quark, molecule)?

quark

The component in a solution that is present in the largest amount

solvent

An iron fence is left unpainted, and it reacts with the oxygen in the air, forming rust. The formation of rust is an example of a(n) _____ reaction.

synthesis

Democritus thought that matter was made of tiny particles

that could not be divided

In an electron dot diagram, the symbol for an element is used to represent

the nucleus and the electrons in the inner energy levels

The Neon atom tends NOT to gain any additional electrons because

there is no room available in its outermost occupied shell

The formation of an ionic bond involves the

transfer of electrons