Atomic Structure And The Periodic Table Flashcards
What are all substances made from?
Atoms
What is an atom?
The smallest part of an element that can exist
Atoms of each element are represented by what?
A chemical symbol
How many different elements are there and where are they shown?
There are about 100 different elements. Elements are shown in the periodic table
What are compounds formed from?
They are formed from elements by chemical reactions
What do chemical reactions always involve?
Chemical reactions always involve the formation of one or more new substances and often involve a detectable energy change
What do compounds contain?
Compounds contains two or more elements chemically combined in fixed proportions
How can compounds be represented?
Compounds can be represented by formulae using the symbols of the atoms from which they were formed
How can compounds be separated?
Compounds can only be separated into elements by chemical reactions
What does the nucleus in an atom contain?
It contains protons and neutrons
Why does the nucleus in an atom have a positive charge?
It has a positive charge because of the protons
How do the electrons move around the atom?
They move around the nucleus in electron shells
Are electrons positively or negatively charged?
They are negatively charged and tiny but they cover a lot of space
Do electrons have a mass?
They have virtually no mass
Where is almost all of the mass of an atom?
In the nucleus
What does the sum of the protons and neutrons in an atom create?
Its mass number
Atoms of the same element can have different numbers of neutrons. What are these atoms called?
Isotopes of that element
Is the mass number the top number or bottom number?
The top number
Is the atomic number the top number or the bottom number?
The bottom number
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
Very small
What is a proton’s relative charge?
+1
What is a neutron’s relative charge?
0
What is an electron’s positive charge?
-1
In an atom what is the number of electrons is equal to?
The number of electrons is equal to the number of protons in the nucleus
Do you atoms have an overall electrical charge?
No
What does the atomic number represent?
The number of protons in an atom
Why do atoms not have an overall electrical charge?
Because they have the same number of protons as electrons
What does the mass number represent?
The mass number represents the total number of protons and neutrons in the atom
How do you work out the number of neutrons in an atom?
Subtract the atomic number from the mass number
Why does the charge cancel out in an atom?
Because the charge on the electrons is the same size as the charge on the protons but opposite so the charges cancel out
Why do ions have an overall charge?
Because in an ion the number of protons doesn’t equal the number of electrons
What is an ion?
An ion is an atom or group of atoms that have lost or gained electrons
How big is the radius of a nucleus in an atom?
1×10 to the power of -14
The radius of the nucleus is less than how much of that of the atom?
1 out of 10,000
What are isotopes?
Different forms of the same element, which have the same number of protons but different number of neutrons
Isotopes of the same except for what?
Extra neutrons
Isotopes have the same atomic number but different what?
Different mass numbers
What do mixtures consist of?
A mixture consists of two or more elements or compounds not chemically combined together
The chemical properties of each substance in the mixture are what?
Unchanged
How can mixtures be separated?
Physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography
When mixtures are separated by physical processes it does not involve chemical reactions so are any new substances made?
There are no new substances made
Unlike in a compound, there’s no what between the different parts of a mixture?
There is no chemical bond
What were atoms thought to be like before the discovery of the electron?
Atoms were thought to be tiny spheres that could not be divided
What did the discovery of the electron lead to?
It led to the plum pudding model of the atom
The plum pudding model suggests that the atom is a ball of positive charge with what embedded in it?
Negative electrons
The results from what experiment led to the conclusion that the mass of an atom was concentrated at the nucleus and that the nucleus was charged?
Alpha particle scattering experiment
What replaced the plum pudding model?
The nuclear model
Who adapted the nuclear model?
Niels Bohr
How did Niels Bohr adapt the nuclear model?
By suggesting that electrons orbit the nucleus at specific distances
What did later experiments lead to? What was the name of the particles?
The idea 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. The name proton was given to these particles
The experimental work of who provided the evidence to show the existence of what within the nucleus
James Chadwick provided the evidence to show the existence of neutrons within the nucleus
At the start of which century did who describe atoms as solid spheres and said that different spheres made up the different elements?
At the start of the 19th century John Dalton
In 1897 who concluded from his experiments that atoms weren’t solid spheres?
JJ Thomson
JJ Thompson’s measurements of charge and mass showed that an atom must contain what?
Even smaller, negatively charged particles- electrons
Who conducted the famous alpha particle scattering experiment in 1909?
Ernest Rutherford and his student Ernest Marsden
How did Ernest Rutherford and Ernest Marsden conduct the alpha particle scattering experiment?
They fired positively charged alpha particles at an extremely thin sheet of gold