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Topic 1 – Atomic Structure and the Periodic Table Revision Checklist

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1 Topic 1 – Atomic Structure and the Periodic Table Revision Checklist
Subtopic Class Notes Revision Notes Past Exam Questions C2.1 Mendeleev C2.2 Structure of an atom C2.3 The modern periodic table C2.4 Electron shells

2 The history of the periodic table
C2.1 Mendeleev The history of the periodic table 1798: Lavoisier began to divide the elements into metals and non-metals. 1860: 63 elements were known. John Newlands noticed that when the elements were put in order of atomic mass, that every eighth element had similar properties. But this only worked as far as calcium

3 1871: Mendeleev C2.1 Mendeleev
Mendeleev arranged the elements in order of atomic mass He arranged the elements so that elements with similar properties were in the same vertical columns (groups). He thought there must still be some elements to discover so left gaps for them. He used the gaps to predict the properties of the undiscovered elements. For example he predicted the properties of Eka Aluminium (what we now know as Gallium)

4 C2.2 Structure of an atom Elements Definition…Element: A element is made up of only one type one atom. It cannot be spilt into simpler substances These atoms are ALL iron – there’s nothing else in here

5 Boardworks GCSE Additional Science: Physics Radioactive Decay
C2.2 Structure of an atom Atomic Structure Ideas about atomic structure have changed over time. In 1803, John Dalton said atoms were solid spheres of matter that could not be split. Dalton also suggested that each element contained identical atoms.

6 Boardworks GCSE Additional Science: Physics Radioactive Decay
C2.2 Structure of an atom In 1897, whilst studying cathode rays, JJ Thomson discovered tiny particles with a negative charge. His discovery did not fit with Dalton’s model of the atom. Photo credit: The Cavendish Laboratory, University of Cambridge nucleus Ernest Rutherford suggested that an atom is mostly empty space with its positive charge and most of its mass in a tiny central nucleus. Electrons orbited this nucleus at a distance, like planets around the Sun. electrons

7 Atomic Structure nucleus electron neutron proton
C2.2 Structure of an atom Atomic Structure nucleus electron proton neutron

8 C2.2 Structure of an atom There are two properties of subatomic particles that are especially important: 1. Mass 2. Electrical charge 1 +1 1 almost 0 -1 The atoms of an element contain equal numbers of protons and electrons and so have no overall charge.

9 C2.3 The modern periodic table
How many protons? The atoms of any particular element always contain the same number of protons. For example: hydrogen atoms always contain 1 proton; carbon atoms always contain 6 protons; magnesium atoms always contain 12 protons, The number of protons in an atom is known as its atomic number or proton number. It is the smaller of the two numbers shown in most periodic tables.

10 C2.3 The modern periodic table
Mass number Electrons have a mass of almost zero, which means that the mass of each atom results almost entirely from the number of protons and neutrons in the nucleus. The sum of the protons and neutrons in an atom’s nucleus is the mass number. It is the larger of the two numbers shown in most periodic tables. 1 1 3 4 7 13 14 27

11 Relative Atomic Mass The actual mass of a hydrogen atom is 1.7x10-24g
C2.3 The modern periodic table Relative Atomic Mass The actual mass of a hydrogen atom is 1.7x10-24g (that’s g!) Far too small a number to easily get your head around… So – we use Relative Atomic Mass instead (Ar) We compare the mass of each element to carbon-12 Carbon 12 has 6 protons and 6 neutrons so we say its Ar = 12 Magnesium has the same mass as 2 carbon atoms so we say its Ar = 24

12 Why does chlorine have an Ar of 35.5?
C2.3 The modern periodic table Why does chlorine have an Ar of 35.5? …because there are different isotopes of chlorine

13 Isotopes always have the same atomic number, but different mass number
C2.3 The modern periodic table …have the same number of protons and electrons, but different numbers of neutrons. E.g. hydrogen has 3 isotopes… Isotopes H 1 2 3 Hydrogen Deuterium Tritium Isotopes always have the same atomic number, but different mass number

14 C2.3 The modern periodic table
Chlorine always has 17 protons, but some have 18 neutrons, others have 20 neutrons Isotopes The relative abundance (proportion) of Chlorine-35 is 75% The relative abundance (proportion) of Chlorine-37 is 25% We can use the Ar and relative abundance of the isotopes to work out the Ar of the element.

15 Q1: Calculate the Ar of Neon
C2.3 The modern periodic table Example: Isotopes The relative abundance (proportion) of Chlorine-35 is 75% The relative abundance (proportion) of Chlorine-37 is 25% Q1: Calculate the Ar of Neon

16 Q1: Calculate the Ar of Neon
C2.3 The modern periodic table Q1: Calculate the Ar of Neon Q2: Calculate the Ar of Lithium Q3: Calculate the Ar of Iron Q4: Calculate the Ar of Silicon Q5: Calculate the Ar of Mercury The table shows the natural relative abundance of the main isotopes of mercury, Hg. Mass number % Relative abundance

17 The Modern Periodic Table
C2.3 The modern periodic table The Modern Periodic Table Elements are arranged in order or increasing atomic number (number of protons) Horizontal rows are called periods Vertical rows are called groups (the period number tells you the number of electron shells) Elements in the same group have similar properties (because they have the same number of outer electrons) Most elements are metals (in yellow on the left), non-metals are shaded in blue

18 Electronic Structure 2.8.1 Electrons are held in shells
C2.4 Electron shells Electronic Structure No. of electrons in 2nd shell 2.8.1 No. of electrons in 3rd hell No. of electrons in 1st shell Electrons are held in shells The first shell can hold upto 2 electrons The second shell can hold upto 8 electrons The third shell can hold upto 8 electrons


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