Atomic structure and the periodic table Flashcards
Define the word ‘element’ in terms of atoms
An element is made up of atoms of the same type
How many elements are shown in the periodic table?
118
What is a compound and how are they represented?
A compound is a substance that contains 2 or more elements that are chemically combined. It is represented using a formula (symbols)
How are compounds formed and separated? What does this involve?
Compounds are formed by chemical reaction in which bonds are formed and an entirely new substance is created.
To separate a compound, energy must be added in the form or heat or electricity.
What are the group 1 & 7 elements known as?
Group 1 elements are known as alkali metals.
Group 7 are known as the halogens.
How do you balance equations?
Use a table
What is a mixture? Are the properties of each substance in the mixture changes or unchanged?
A mixture is 2 or more elements which have not been chemically bonded, meaning the properties of each substance stay the same.
What are the 5 processes which can be used to separate mixtures? (for each process state the mixtures it can be used to seperate)
The 5 processes are:
filtration - insoluble solids from liquids
crystallisation - solids from solutions
simple distillation - a liquid from a solution
fractional distillation- liquids that have different boiling points
chromatography - separate dyes
What is filtration?
The physical process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium that permits the fluid to pass through but retains the solid particles.
What is Crystallisation?
A method for transforming a solution into a solid.
What is Chromatography?
A process for separating components of a mixture
What is simple distillation?
It separates a liquid and soluble solids from a solution or a pure liquid from a mixture of liquids
what is fractional distillation?
It is the separation of a mixture into its component parts (fractions)
What lead to a scientific model being changed or replaced?
the data did not agree with their predictions resulting in the model being changed
How did the model of the atom change as new evidence was discovered?
the plum pudding model suggested that the atom was a ball of positive charge with electrons embedded in it the scattering experiment led to a change of the model of the atom being changed as electrons were discovered to orbit the nucleus
What were the roles of Niels Bohr and James Chadwick in the development of the model of the atom?
James identified the neutron.
Niels proposed the theory for the hydrogen atom
Why did the new evidence from the scattering experiment led to a change in the atomic model?
When firing atoms through foil, some particles passed through and some rebounded. This proved that electrons orbited the nucleus.
What are the relative charges of protons, neutrons and electrons?
Protons - +1
Neutrons - 0
Electrons - -1
Why do atoms have no overall electrical charge?
Because they have an equal amount of protons and neutrons
What does atomic number represent?
number of protons in the nucleus of an atom
How do atoms of different elements differ from each other?
by the number of protons
What is the structure of atoms?
Inside the nucleus there are neutrons and protons and orbiting the nucleus there are electrons
What is the radius of an atom?
0.1nm or 1x10 to the power of -10m
What is the radius of a nucleus?
1x10 to the power of -14m
Where is most of the mass of an atom?
the nucleus
What are the relative masses of the protons, neutrons and electrons?
proton = 1
neutron = 1
electron = 1/1840 or 0
What does mass number represent?
the combined number of protons and neutrons
What is an isotope and what are their differences and similarities to each other?
atoms with the same number of protons but different number of neutrons
How do you use the mass number and atomic number to calculate the number of protons, neutrons and electrons in an atom or ion?
mass number - atomic number =number of neutrons
atomic number = number of protons
number of protons = number of neutrons
What is relative atomic mass and how is it calculated?
The relative atomic mass of an element is the average mass of its atoms.
Isotopic mass x relative abundance/100 + isotopic mass x relative abundance/100
How are elements in the periodic table arranged and why is it called the periodic table?
In order of increasing atomic number
as the rows go down, a new ring is added to the outside of the nucleus
its organised based on properties of the elements
How does reactivity relate to elements positions in the periodic table?
reactivity decreases as you go from left to right across a period
How did scientists initially classify elements?
they arranged them in order of atomic weight
What were problems with the early periodic table?
it was incomplete since many elements were unknown
How did mendeleev overcome the early problems of the periodic table?
he left gaps for the yet to be discovered elements
How was Mendeleev proved right and why was the initial order based on atomic weights not always correct?
when they discovered isotopes of the same element it explained why some atoms had heavier atomic masses than expected
Where do metals and non-metals appear in the periodic table?
metals are to the far left of the ladder line and nonmetals are to the right
What is the type of ion metals form?
they form positive ions
What is the type of ion non-metals form?
they form negative ions
What are the physical and chemical properties of metals?
malleable, ductile, good conductors of heat and electricity
What are the physical and chemical properties of non-metals?
brittle, bad conductors of heat and electricity, they are not strong
How are the reactions of elements related to the arrangement of electrons in their atoms and their atomic number?
the number of outer shell electrons in the reacting atoms
Why are the noble gases unreactive in terms of their outer electrons?
they already have complete outer shells so they have no tendency to lose gain or share electrons
What is the trend in boiling point going down group 0?
it increases
What is the electronic structure of the alkali metals and how do their properties depend on this?
they all have one electron in their outer shell
What are the reactions of the first 3 alkali metals with oxygen?
lithium - relatively slow
sodium - quicker than lithium
potassium - so quick its hard to see that its actually a shiny metal
What are the reactions of the first 3 alkali metals with chlorine?
lithium - reddish flame + white solid is produced
sodium - yellowish flame + white solid is produced
potassium - purplish flame + white solid is produced
What are the reactions with the first 3 alkali metals with water?
lithium - slowly fizzes until is disappears
sodium - fizzes rapidly and disappears faster
potassium - burns violently with a purple flame and disappears extremely quickly
What is the trend in reactivity going down group 1?
it increases
What is the electronic structure of the halogens and how do their properties depend on this?
they are all one electron short of having a full outer shell which makes them very reactive
What type of element are the halogens and what do their molecules consist of?
two halogen atoms joined by a single covalent bond
What are the type of compounds are formed when halogens react with metals?
ionic compounds
What are the type of compounds are formed when halogens react with non-metals?
molecular compounds
What is the trend in reactivity going down the halogens?
they get less reactive
What are the transition elements?
central block of the periodic table between group 2 and group 3
what are the typical properties of transition elements?
high melting and boiling points
