Radiation
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118 Terms
What is an atom?
The smallest unit of an element that still has the properties of that element.
What are the three main subatomic particles?
Protons, neutrons and electrons.
Where are protons found?
In the nucleus.
Where are neutrons found?
In the nucleus.
Where are electrons found?
In electron shells/clouds surrounding the nucleus.
What charge does a proton have?
Positive (+1).
What charge does a neutron have?
Neutral (0).
What charge does an electron have?
Negative (−1).
Which subatomic particle determines the identity of an element?
The number of protons.
Which subatomic particle has the smallest mass?
The electron.
What is the relative mass of a proton?
About 1.
What is the relative mass of a neutron?
About 1.
What is the relative mass of an electron?
About 1/2000 of a proton, so it is usually treated as having almost no mass.
What is the atomic number?
The number of protons in an atom.
Why does the atomic number identify an element?
Every element has a unique number of protons.
What is the mass number?
The total number of protons + neutrons.
How do you calculate the number of neutrons?
Mass number − atomic number.
Example: carbon has mass number 12 and atomic number 6. How many neutrons?
12 − 6 = 6 neutrons.
In a neutral atom, how do protons and electrons compare?
They are equal in number.
Why is a neutral atom uncharged?
The positive proton charges and negative electron charges cancel out.
What is an ion?
An atom with an overall electrical charge because it has gained or lost electrons.
How does an atom become a positive ion (cation)?
It loses electrons, leaving more protons than electrons.
How does an atom become a negative ion (anion)?
It gains electrons, giving it more electrons than protons.
What happens when a particle loses electrons?
It becomes more positive.
What happens when a particle gains electrons?
It becomes more negative.
What is the charge of an atom with 12 protons and 10 electrons?
2+.
What is the charge of an atom with 16 protons and 18 electrons?
2−.
What is a sulfide ion?
S²⁻, formed when sulfur gains 2 electrons.
What happens when two positively charged particles are brought close together?
They repel each other.
What happens when a positive and negative particle are brought close together?
They attract each other.
What happens between two negative charges?
They repel each other.
What is the basic rule for electric charges?
Like charges repel; opposite charges attract.
What is the Periodic Table?
A table that organises all known chemical elements.
What does each element's symbol represent?
A shortened form of its element name.
What is an element?
A pure substance made of only one type of atom.
What is a group on the Periodic Table?
A vertical column.
What is a period on the Periodic Table?
A horizontal row.
What do elements in the same group generally have?
Similar chemical properties.
What does the period number tell you about an atom?
The number of occupied electron shells.
What are valence electrons?
Electrons in the outermost occupied electron shell.
How many electron shells does carbon have?
2.
How many valence electrons does carbon have?
4.
What is carbon's atomic number?
6.
How many protons does carbon have?
6.
How many electrons does neutral carbon have?
6.
How many neutrons does carbon-12 have?
6.
What are the two main regions of an atom?
The nucleus and the electron shells/cloud.
What is found in the nucleus?
Protons and neutrons.
What is found outside the nucleus?
Electrons.
What evidence showed that atoms contain smaller charged particles?
Experiments such as cathode-ray experiments helped scientists discover electrons, while atomic models and later experiments showed that atoms contain a small positive nucleus.
What did Rutherford's gold foil experiment help show?
That atoms have a tiny, dense, positively charged nucleus and are mostly empty space.
What is the Law of Conservation of Mass?
Mass is not created or destroyed during a chemical reaction.
What does conservation of mass mean for a chemical equation?
The same atoms must be present before and after the reaction.
What happens to atoms during a chemical reaction?
They are rearranged into new combinations.
Are atoms created or destroyed in a chemical reaction?
No.
What happens to chemical bonds during a reaction?
Old bonds are broken and new bonds form.
What happens to energy when bonds break?
Energy is absorbed.
What happens to energy when new bonds form?
Energy is released.
What are reactants?
The substances present at the start of a chemical reaction.
Where are reactants written in an equation?
On the left side of the arrow.
What are products?
The new substances formed in a chemical reaction.
Where are products written in an equation?
On the right side of the arrow.
What does → mean in a chemical equation?
Produces or forms.
What is an exothermic reaction?
A reaction that releases energy to the surroundings.
What happens when magnesium burns?
It undergoes combustion and releases energy.
What is an acid + metal reaction?
Acid + metal → salt + hydrogen.
Example of an acid + metal reaction?
Zinc + hydrochloric acid → zinc chloride + hydrogen.
What is an acid + base reaction?
Acid + base → salt + water.
What is neutralisation?
An acid reacting with a base to form salt and water.
Example of a neutralisation reaction?
Sodium hydroxide + hydrochloric acid → sodium chloride + water.
What is an acid + metal carbonate reaction?
Acid + metal carbonate → salt + water + carbon dioxide.
Example of an acid + metal carbonate reaction?
Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide.
What is combustion?
A reaction where a substance burns in oxygen.
What are the products of methane combustion?
Carbon dioxide and water.
What is the word equation for methane combustion?
Methane + oxygen → carbon dioxide + water.
What is corrosion?
A reaction where a metal reacts with substances such as oxygen and water.
What forms when iron corrodes?
Iron(III) oxide (rust).
What are the main reaction types studied here?
Acid + metal, acid + base, acid + metal carbonate, combustion and corrosion.
How is a salt named after an acid?
The acid determines the ending of the salt's name.
Hydrochloric acid forms what type of salt?
Chloride.
Sulfuric acid forms what type of salt?
Sulfate.
Nitric acid forms what type of salt?
Nitrate.
What salt forms when hydrochloric acid reacts with zinc?
Zinc chloride (ZnCl₂).
What salt forms when sulfuric acid reacts with calcium carbonate?
Calcium sulfate (CaSO₄).
What salt forms when nitric acid reacts with sodium hydroxide?
Sodium nitrate (NaNO₃).
What are the three stages of writing a chemical equation?
Word equation → symbol equation → balanced equation.
What is a word equation?
An equation written using the names of substances.
What is a symbol equation?
An equation written using chemical formulas.
What is a balanced equation?
An equation with the same number of each type of atom on both sides.
What is a coefficient?
The big number placed in front of a chemical formula.
What does a coefficient change?
The number of molecules/formula units present.
What is a subscript?
The small number within a chemical formula showing how many atoms of an element are present.
Can you change a subscript when balancing an equation?
No. It would change the substance.
Can you change a coefficient when balancing an equation?
Yes.
What does 2H₂O mean?
2 molecules of water.
How many hydrogen atoms are in 2H₂O?
4 hydrogen atoms.
How many oxygen atoms are in 2H₂O?
2 oxygen atoms.
What are the steps for balancing an equation?
Write formulas, count atoms on both sides, add coefficients, then re-count to check.
What should you do first when balancing?
Write the correct chemical formulas.
What should you never change when balancing?
The subscripts.