4.1 A Simple Model Of The Atom Symbols Relative Atomic Mass Electronic Charge And Isoptopes Flashcards
What are all substances made of?
Atoms
What is an atom?
The smallest part of an element that can exist
How are each atoms of each element represented?
By a chemical symbol
How many different elements are there?
About 100
Where are elements shown?
In the periodic table
How are compounds formed from elements?
By chemical reactions
What do chemical reactions always involve?
The formation of one or more new substances and often involve a detectable energy change
What do compounds contain?
Two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they formed
How can compounds be separated into elements?
By chemical reactions
What does a mixture consist of?
2 or more elements or compounds not chemically combined together
In a mixture are the chemical properties of each substance changed or unchanged?
Unchanged
How can mixtures be separated?
By physical processes such as filtration crystallisation simple distillation, fractional distillation and chromatography
Do the physical processes involve chemical reactions and new substances being formed?
No
Describe the process of filtration?
Pour the mixture of solid and liquid through the filter paper in a funnel.
The filter paper separates the solvent (liquid) from the solute (solid).
The clear liquid (filtrate) is obtained in the beaker and the solid (residue) traps on the paper.
Describe the process of crystallisation
The solution is heated in an open container.
The solvent molecules start evaporating, leaving behind the solutes.
When the solution cools, crystals of solute start accumulating on the surface of the solution.
Crystals are collected and dried as per the product requirement.
Describe the process of distillation
Salt solution is heated.
Water evaporates and its vapours rise. The water vapour passes into the condenser, where it cools and condenses. Liquid water drips into a beaker.
All the water has evaporated from the salt solution, leaving the salt behind.
Describe the process of chromatography
Start by drawing a baseline on the chromatography paper using a pencil. …
Place a small spot of the sample mixture on the baseline.
Pour the solvent into a beaker. …
Allow the solvent to slowly travel upwards through the paper, taking with it a few soluble pigments from the sample mixture.
Describe the process of fractional distillation
Step 1:- The mixture of liquids is heated in a round-bottomed flask, and the vapours rise and enter the fractionating column.
Step 2:- The vapours then move to the condenser where the temperature is low.
Step 3:- The vapours cool down and get converted into liquid form.
What is fractional distillation used to separate?
Miscible liquids
What were atoms thought to be before the discovery of the electron?
To be tiny spheres that could not be divided
What did the discovery of the electron lead to ?
The plum pudding model of the atom
What does the plum pudding model suggest?
The atom is a ball of positive charge with negative electrons embedded in it
What was the result of the alpha particle scattering led to?
The conclusion that the mass of an atom was concentrated at the centre and that the nucleus was charged
How did Niels Bohr adapt the nuclear model?
By suggesting that electrons orbit the nucleus at specific distances
What is a proton?
A tiny positive particle found inside the nucleus of an atom
What did later experiments on the atom show?
That the positive charge of any nucleus could be subdivided into a whole number of smaller particles,each particle having the same amount of positive charge
What did the experimental work of James Chadwick provide?
The evidence to show the existence of neutrons within the nucleus
What is a nucleus?
The very small and dense central part of an atom that contains protons and neutrons
What is a neutron?
A dense particle found inside the nucleus of an atom . It is electrically neutral carrying no charge
What is an electron?
A tiny particle with a negative charge . Electrons orbit the nucleus of atoms or ions in shells
Who discovered the electron lead?
Jo Thompson
Who discovered the nucleus and protons?
Rutherford
What are the relative electrical charges of protons neutrons and electrons?
+1 0 -1
What charge do atoms have overall?
No charge
What are the number of electrons in an atom equal to?
The number of protons
What are the number of protons in an atom of an element known as?
Atomic number
All atoms of a particular element have the same number of what?
Protons
What do atoms have approximately a radius of ?
About 0.1nm (1 x 10 to the power of -10m)
What are the relative masses of protons , neutrons and electron?
1 1 very small
What is the sum of the protons and neutrons in an atom known as?
Mass number
What are isotopes?
Atoms of the same element that have the same number of protons but different number of neutrons
How do find the number of neutrons?
Mass number - atomic number
What is an ion ?
A charged particle produced by the loss or gain of electrons
What is the relative atomic mass of an element?
An average value that takes account of the abundance of the isotopes of the element
How is the periodic table arranged?
In order of atomic number and so that elements with similar properties are in columns known as groups
Why is the periodic table called the periodic table?
Because similar properties occur at regularintervals
What do elements in the same group in the periodic table share?
The same number of electrons in their outer shells and this gives them similar properties
Before the protons neutrons and electron were discovered how did scientists classify the elements?
By arranging them in order of their atomic weights
What happened if the strict order of atomic weights was followed for the periodic table?
Some elements were placed in appropriate groups
How did Mendeleev over come some of the problems on the periodic table?
By leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights
What were the gaps in the periodic table filled by?
Elements with properties predicted by Mendeleev were discovered and filled the gaps
What made it possible to explain why the order based on atomic weights was not always correct?
Isotopes
What are metals?
Elements that react to form positively ions
What are non metals?
Elements that do not form positive ions
What are the majority of elements?
Metals
Where are metals found in the periodic table?
To the left and towards the bottom of the periodic table
Where are non metals found in the periodic table?
Towards the right and top
What are the elements in group 0 called?
Noble gases
What some properties of noble gases ?
They are unreactive and do not easily form molecules
Why don’t noble gases form molecules easily?
Because their atoms have stable arrangements of electrons
How many electrons are there in the outer shell for noble gases?
8 except from helium which has 2
How do the boiling point of noble gases increase ?
With increasing relative atomic mass
What are the elements in group 1 known as ?
Alkali metals
Why do alkali metals have characteristic properties?
Because of the single electron in their outer shells
What happens when alkali metals react with water ?
The metal floats around the water fizzing which happens because the metal reacts with the water to form hydrogen gas
What happens when u react potassium with water?
Reacts vigorously with water that the hydrogen produced ignites with a lilac flame
What happens when alkali metals react with chlorine?
They react vigorously with chlorine and produce metal oxides
How does the reactivity of alkaline metals increase?
With increasing relative atomic mass
What are the elements in group 7 known as?
Halogens
Why do group 7 metals have similar reactions?
Because the all have 7 electrons in their outer shells
What are halogens and what do they consist of?
Non metals and consist of molecules made of pairs of atoms
What happens to halogens with increasing relative atomic mass?
The higher its relative molecular mass melting point and boiling point
What happens to the reactivity of ehalogens with increasing relative atomic mass?
It decreases
What can a more reactive halogen do to a less reactive halogen from an aqueous solution of its salt?
It can displace it
What happens to halogens when reacted to metals?
They form ions with a single negative charge in their ionic compounds with metals
What happens to halogens when reacted with a non metals ?
They form covalent compounds by sharing electrons with other non metals
Where are transition elements?
Metals with similar properties which are different from those of the elements in group 1
What are the difference between transition metals and group 1 metals?
Transition metals have higher melting point and density
Stronger and harder
Less reactive
Do not react vigorously with water or oxygen
Can form ions with different charges in compounds that are often coloured
Important industrial catalyst
What do many transition metals have ?
Ions with different charges form coloured compounds and are useful as catalysts
