rmg'kwjw Flashcards by Unknown Unknown

how are compounds created ?

when different elements link together in definite proportions

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How many molecules are in the following element:

CH4
methane

1 carbon molecule (C)

bonded to 4 hydrogen molecules (H) (4)

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Chemical bonding involves the ________ _______ of each atom

Outer electrons

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the outer electrons are used to _______

form chemical bonds

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How to determine if something is an element or not ?

Elements cannot be further broken down to a simpler form and are listed on the periodic table

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These OUTERMOST electrons are the only electrons that form chemical bonds

name them

Valence electrons

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the ____ of valence electrons in an atom helps determine the type and ______of _____ the atoms can form

A. Type / form / bonds
B. Number / form / bonds
C. Number / number / bonds

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how can the periodic table tell you the number of valence electrons an atom has ??

Group 1 has 1 valence electron
Group 2 has 2 valence electrons
Group 3 has 3 valence electrons
Group 4 has 4 valence electrons

etc..

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atoms with _ valence electrons are chemically ______. They do not react easily with other atoms

stable

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by forming bonds atoms become … ?

more chemically stable

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Fe58 26

deduce the number of electrons , protons and neutrons

electrons: 26
protons: 26
neutrons: 32

(Electron and proton number are the same and to find the number of neutrons subtract 26 from 58 = 32)

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Covalent bonds is between …?

non-metals

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Ionic bond is between … ?

at least 1 metal and non metal(s)

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Metallic bond is between … ?

metals

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why is the formula for hydrogen always written as H2

it is a diatomic gas (‘di’ meaning 2)

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iron is a transition metal , state two things about iron

iron forms coloured compounds

iron can act as a catalyst

iron is brown when freshly cut

(remember any two)

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ionic compounds consist of ..?

positive metal ion and negative non metal ion = net charge of 0

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metallic elements tend to ____ electrons

lose

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nonmetals tend to ____ electrons

gains

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cations are …?

metallic elements.

positively charged ions (meaning they have more protons then electrons due to LOSING one or more electrons)

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anions are … ?

nonmetals.

negatively charged ions (due to having GAINED one or more electrons)

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Complete the chemical equation for this reaction……………….+ 2KI →I2+ ……………KCl

CL2 + 2KL –> l2+ 2KCl

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4.Which process involves a physical change? 
A. heating calcium carbonate 
B. burning wood 
C. melting an ice cube
D. mixing an acid and a base

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5.Which element is a non-metal? 
A scandium 
B sodium 
C strontium 
D sulfur

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``` Some plastics are non-biodegradable. What is the meaning of the term non-biodegradable? A cannot be recycled for further use B gives off greenhouse gases when burnt C harmful to animals and plants D not broken down by natural processes ```

Which statement about silicon dioxide, SiO2, is correct? A It conducts electricity because it contains free electrons. B it is a macromolecule with four oxygen atoms bonded to each silicon atom. C It is a simple covalent molecule. D Its structure is similar to graphite.

How can you model the valence electrons of metal atoms?

Sea of electrons

Why are metals good conductors ?

Metals are good conductors of electric current because electrons can flow freely in the metal.

Which metals have a hexagonal close-packed crystal structure

magnesium zinc cadmium etc...

What are alloys ?

mixture of two or more elements and at least one of them is a metal

example of an alloy ?

Brass | combination of copper and zinc

Does diamond conduct electricity ?

No diamond does not conduct electricity because it is a non-metallic element

diamond has a very ____ _______ point

high melting

carbon doesn't conduct electricity. Carbon, graphite and diamond have the same giant molecular crystal structures. Does *graphite* conduct electricity ?

Graphite is a form of carbon that *does* conduct electricity

why can graphite be used as a lubricant / feel slippery

because between the layers of sheets, there are weaker forces of attraction. This means that the layers are able to slide over each other easily.

What names would you give these compounds? 1) NaI 2) MgS 3) NO

1) sodium iodide 2) magnesium sulphide 3) Nitrogen oxide

how to determine if something is in -ite -ate or -ide

______ide is used for non-metal compounds generally ______ate and _____ite is used for polyatomic ions of oxygen. -ate is used for the ion that has the largest number of Oxygen atoms. -Ite is used for the ion that has the smallest number of oxygen atoms

during a chemical change the composition of matter ______ changes

always

A substance present at the start of the reaction is a ..?

reactant

substance produced in the reaction is a ..?

product

During a physical change, the composition of the matter _____ changes.

never

what are four clues a chemical change has taken place ?

1. transfer of energy 2. change in colour 3. the production of gas 4. formation of a precipitate

transfer of energy is ?

exothermic

gaining of energy is ?

endothermic

Why is diamond much harder than graphite?

because of the covalent bonds that extend in all directions through the crystal.

Why can graphite Conduct electricity

Because of the different carbon arrangements

``` What is the symbol of the metal used in the manufacture of aircraft because of its strength and low density? A. Al B. Cu C. Fe D. Zn ```

answer A. = aluminum

Rusting of an article made up of iron is called A. corrosion and it is a physical as well as chemical change B. dissolution and it is a physical change C. corrosion and it is a chemical change D. dissolution and it is a chemical change

Which of the following are physical changes? (i) Melting of iron metal (ii) Rusting of iron (iii) Bending of an iron rod (iv) Drawing a wire of iron metal A (i), (ii) and (iii) B (i), (ii) and (iv) C(i), (iii) and (iv) D(ii), (iii) and (iv)

Bronze is used for making medals .A True B False

``` Which of the following models can describe the valence electrons of metals? A. A body -centered cube B. Octets of electrons C. A rigid array of electrons D. A sea of electrons ```

Alloys usually consists of more than one metal combined A. True B. False

false

``` The “lead” in a pencil is made of a mixture of graphite and clay. When the percentage of graphite is increased, the pencil slides across the paper more easily.Which statement explains this observation? A. Graphite has a high melting point B. Graphite is a form of Carbon C. Graphite is a lubricant D, Graphite is a non –metal ```

what are beakers used for ?

hold solids and liquids but they are not accurate so they are used to measure the volume of things

what are bunsen burners used for ?

heating non-volatile liquids and solids

rmg'kwjw Flashcards

(55 cards)