4.1-Atomic Structure and the periodic table

Question 1

What is an atom?

Answer 1

An atom is the smallest part of an element that can exist.

Question 2

What is an element?

Answer 2

An element is a substance that is made of only one type of atom. Elements can exist as single atoms, molecules or giant structures.

Question 3

Where are the elements found?

Answer 3

Each element can be found on the periodic table, and there are about 100 atoms. Each one can be represented by its own symbol and has its own individual name.

Question 4

What is a compound?

Answer 4

A compound contains two or more elements chemically combined in fixed proportions. Compounds can only be separated through a chemical reaction.

Question 5

How do you name elements?

Answer 5

find the symbol on the periodic table, and use its name

Question 6

How do you name compounds with a metal and a non-metal?

Answer 6

never change the name of the metal (always written first) The non metals ending changes to ide.

Question 7

How do you name compounds with two non-metals?

Answer 7

name of the first element stays the same, and the ending of the second element changes to ide. If there are two of the second element, then add a di in front (eg. carbon dioxide)

Question 8

How do you name a compound with a metal and two non-metals (where one is oxygen)

Answer 8

ending of the non-metal (that is not oxygen) changes to ate.

Question 9

What do chemical reactions show?

Answer 9

Chemical equations show the reactants (the substances you start with) and products (the substances made) in a reaction.

Question 10

How can you represent chemical reactions?

Answer 10

You can represent reactions as word equations or symbol equations.

Question 11

What happens in a chemical reaction?

Answer 11

In chemical reactions, the atoms get rearranged and are bonded together.

Question 12

What do balanced symbol equations help you to see?

Answer 12

Using symbol equations helps you see how much of each substance is involved in a reaction.
If an equation is balanced, there is the same number of each type of atom on both sides of the equation.
This is important, because atoms cannot be created or destroyed in a chemical reaction.

Question 13

What is the law of conservation of mass?

Answer 13

The total mass of the products formed in a reaction is equal to the total mass of the reactants.

Question 14

What are the state symbols?

Answer 14

(s)-solids
(l)-liquids
(g)-gases
(aq)- aqueous solutions- substances that are dissolved in water

Question 15

What is a mixture?

Answer 15

A mixture consists of two or more elements or compounds not chemically combined together. The properties of each substance in the mixture are unchanged.

Question 16

What are the differences between compounds and mixtures?

Answer 16

-Compounds have a fixed proportion, but mixtures do not
-Mixtures can be separated using physical separation, whereas compounds are separated using chemical separation
-There are chemical bonds in a compounds, but there aren’t in a mixture

Question 17

What is filtration used to separate?

Answer 17

Filtration is used to separate an insoluble solid from a liquid.

Question 18

Method for filtration?

Answer 18

First, the apparatus must be set up with the filter paper sitting in the filter funnel above a flask or beaker. Then, the mixture needing to be separated must be poured into the filter paper

Question 19

Why does filtration work?

Answer 19

The liquid particles are small enough to pass through the filter paper, but the solid particles are too large to fit through the filter paper and so are left behind. The solid left behind is called the residue, and the liquid in the beaker is called the filtrate.

Question 20

What is crystalisation used to separate?

Answer 20

Crystallization is used to separate a soluble solid from a liquid.

Question 21

Method for crystalisation?

Answer 21

A solution is placed in an evaporating basin and heated with a bunsen burner. As the solution is heated, the water in the solution evaporates and this means that the amount of water in the solution will decrease as it turns into a gas and escapes into the air. As this happens, the solid particles which were dissolved in the water are left behind. Once all of the water has evaporated, the solid is left behind on the bottom and sides of the evaporating basin.

Question 22

What is simple distillation used for?

Answer 22

Simple distillation is used to separate a liquid solvent from a dissolved solid.

Question 23

Method for simple distillation?

Answer 23

Set up the apparatus so that the solution in the flask is fitted with a condenser so that any of the gases produced travel through the condenser. The solution is then heated with a bunsen burner. As the water heats up, it evaporates and its vapors rise and pass through the condenser. The condenser is surrounded with cold water and so the water vapor molecules cool down and turn back into a liquid as they travel through the condenser. Liquid water droplets are collected in the beaker at the end. Once all of the water has been collected, the salt that was dissolved in the solution will also be left behind in the flask.

Question 24

What is fractional distillation used for?

Answer 24

Fractional distillation is used to separate two or more liquids that have different boiling points.

Question 25

Method for fractional distillation?

Answer 25

Step 1:- In this step, mixture is heated, and after heating, it is passed into the fractionating column. Step 2:- The mixture gets converted into vapours, and the various components of the mixture are evaporated at different temperatures. Step 3:- These vapours rise through the column and get condensed as it cools down and the temperature drops. Step 4:- The liquid with the lower melting point is collected at the top and the liquid with the higher melting point is collected at the bottom. The boiling point of separated fractions in the fractionating column increases from top to bottom.

Question 26

What is chromatography used for?

Answer 26

Chromatography is used to separate two or more dissolved solids from a solution.

Question 27

Method for chromatography?

Answer 27

1. Draw a horizontal pencil line 2 cm from the short edge of the chromatography paper. Mark pencil spots at equal intervals across the line but not too close to the end of the paper. 2. Use a glass capillary tube to put a small spot of each colouring on the pencil spots. A small spot ensures that the colouring separates clearly. Label each spot in pencil. 3. Pour about 1 cm³ of water into the beaker. 4. Suspend the paper in the beaker so that bottom edge of the paper dips into the water. 5. Wait for the water solvent to travel at least three quarters of the way up the paper. Remove the paper and draw another pencil line at on the dry part of the paper right next to the wet edge. This is the solvent front, the distance travelled by the solvent. 6. Hang the paper up to dry thoroughly. 7. Calculate the Rf values for each spot. Rf value is calculated by distance travelled by substance / solvent front.

Question 28

What will a pure substance look like on the chromatogram?

Answer 28

A pure substance will only have one spot on the chromatogram, whereas a mixture would produce more than one

Question 29

What is the retention factor (Rf value)

Answer 29

a measure of the position of a component in a chromatographic separation.

Question 30

How do you calculate Rf value?

Answer 30

distance moved by substance / distance moved by solvent

Question 31

What was Rutherford's experiment?

Answer 31

Later on, a scientist named Rutherford did an experiment called the scattering experiment. He aimed a beam of alpha particles at a thin layer of gold foil, which was only a few atoms thick. They expected the alpha particles to travel through the thin foil without being deflected, if the plum pudding model was correct.

Question 32

What is the Plum Pudding model?

Answer 32

The atom was thought to consist of negatively charged electrons (the ‘plums’) in a positively charged ‘dough’ or ‘pudding’ Since electrons have a negative charge, it was reasoned that the rest of the atom would be positive, making the atom neutral overall.

Question 33

What was Rutherford's actual results?

Answer 33

most of the alpha particles travelled through the foil as expected, but a few other particles were deflected in lots of different directions. Some were even deflected back to where they had come from

Question 34

What did Rutherford's results show?

Answer 34

the positive charge was not spread throughout the atom, but instead concentrated in a small area at the centre of each atom. This area was called the nucleus

Question 35

What did Bohr suggest?

Answer 35

He suggested that instead of all the electrons rotating around the nucleus in the same areas, the electrons rotated around the nucleus in fixed energy levels, called shells. He also suggested that the electrons orbited at specific distances away from the nucleus.

Question 36

What did Chadwick discover?

Answer 36

neutrons

Question 37

What is the charge and mass of an electron?

Answer 37

Charge = -1, Mass = negligible

Question 38

What is the charge and mass of a proton?

Answer 38

Charge = +1, Mass = 1

Question 39

What is the charge and mass of a neutron?

Answer 39

Charge = 0, Mass = 1

Question 40

What is the overall charge of an atom?

Answer 40

the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge.

Question 41

What is an element's atomic number?

Answer 41

The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.

Question 42

What is an ion?

Answer 42

An ion is a charged particle. If an atom loses electrons, it becomes a positive ion and if it gains electrons, then it becomes a negative ion. For example, when an oxygen atom loses 2 electrons, it becomes an O2+ ion.

Question 43

What is the size of the atomic radius of an atom?

Answer 43

The atomic radius of the atom (the distance from the center of the atom to the outer edge of the atom) is 0.1 nanometres. This is around 1 x 10-10 m.

Question 44

What is the size of the nucleus of an atom?

Answer 44

The nucleus of an atom is 1/10000 the size of an atom. This is about 1 x 10-14 m.

Question 45

What is the mass number of an atom?

Answer 45

The sum of the protons and neutrons in an element is its mass number.

Question 46

What is an isotope?

Answer 46

Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.

Question 47

What is the relative atomic mass?

Answer 47

Relative atomic mass is the weighted mean mass of an element, taking into account all of the different isotopes and their relative abundance.

Question 48

How do you calculate relative atomic mass?

Answer 48

Relative atomic mass = (mass of the isotope x % abundance) / 100 When you have more than one isotope, the isotopes are multiplied by their corresponding % abundance and then added together and divided by 100.

Question 49

How many electrons can go in each shell?

Answer 49

First shell = 2 electrons Second shell = 8 electrons Third shell = 8 electrons The electronic structure of an atom is written as (number of electrons in first shell, in second shell, in third shell etc.)

Question 50

What does the chemical properties of an element depend on?

Answer 50

The chemical properties of an element depend on how many electrons it has. The way an element reacts is determined by the number of electrons in its outermost shell. Since all the elements in one group have the same number of electrons in their outermost shell, they all react in a similar manner.

Question 51

How are the chemical elements arranged in the periodic table?

Answer 51

The chemical elements are placed in order of their atomic number in the periodic table. This arranges the elements so that they line up in groups (columns) with similar properties. There are 8 main groups in the periodic table. The periodic table also gives a summary of the electronic structures of all the elements. Elements in the same group of the periodic table react in similar ways, since they have the same number of electrons in their outermost shell.

Question 52

Why is the periodic table called the periodic table?

Answer 52

The periodic table is called the periodic table because of the regularly repeating patterns in the properties of elements.

Question 53

How did John Dalton arrange the periodic table?

Answer 53

Arranged elements in order of atomic weights. Published a list of elements in A New System of Chemical Philosophy.

Question 54

How did John Newlands arrange the periodic table?

Answer 54

Ordered known elements by atomic mass. Identified a repeating pattern where every eighth element had similar properties. Assumed all elements had been discovered, leading to inconsistencies. The pattern only worked up to calcium, then broke down. His ideas were ridiculed because elements with different properties were grouped together.

Question 55

How did Mendeleev arrange the periodic table?

Answer 55

Russian chemist Dmitri Mendeleev arranged 50 known elements in order of atomic weights. He arranged them so that a regularly occurring pattern in their properties could be seen Left gaps for undiscovered elements and predicted their properties. (eg. gallium) When new elements were discovered, their properties closely matched his predictions. His table was a major breakthrough in understanding elements.

Question 56

What did the discovery of isotopes mean in relation to the periodic table?

Answer 56

Later, the discovery of isotopes explained why ordering strictly by atomic weight was sometimes incorrect. The modern periodic table arranges elements by atomic number, resolving inconsistencies in Mendeleev’s table

Question 57

How is the modern periodic table arranged?

Answer 57

Elements are arranged in order of atomic number (proton number), not atomic mass. Groups contain elements with similar chemical properties. Mendeleev’s table provided the foundation for the modern periodic table.

Question 58

What are metals and non-metals?

Answer 58

Elements that react to form positive ions are metals, whereas elements that react to form negative ions are non-metals.

Question 59

What are the differences between metals and non-metals?

Answer 59

Metals are generally conductors, whereas non-metals are generally insulators Metals generally have much higher melting and boiling points Non-metals are brittle, whereas metals are malleable and ductile

Question 60

What are noble gases?

Answer 60

elements in Group 0 of the periodic table

Question 61

How reactive are noble gases?

Answer 61

They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons.

Question 62

How many electrons are in the outershell of a noble gas?

Answer 62

The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons.

Question 63

What are the boiling points of noble gases?

Answer 63

The boiling points of noble gases are quite low, and there is a trend going down the group. The boiling points of the noble gases increase with increasing relative atomic mass (going down the group).