Organisation of the periodic tableIB MYP Chemistry: Revision notes
Section 1
How the table is arranged
The periodic table arranges the elements in order of increasing atomic number (the number of protons).
- A vertical column is a group. Groups are numbered 1 to 7, followed by Group 0 (the noble gases)
- A horizontal row is a period
Elements in the same group have similar chemical properties. Properties change gradually across a period.
The table is arranged by atomic number, not by mass, and a period is a row, not a column.
Section 2
Position and electron arrangement
An element's position follows from its electron arrangement.
- The number of outer electrons is the group number
- The number of occupied shells is the period number
Worked example: phosphorus has the electron arrangement 2,8,5. It has 5 outer electrons, so it is in Group 5, and 3 shells, so it is in period 3. Its atomic number is 2 + 8 + 5 = 15.
Elements in the same group have the same number of outer electrons, which is why they react in similar ways.
Add up the numbers in the electron arrangement to find the atomic number.
Section 3
Metals and non-metals
Most elements are metals, found on the left and in the middle of the table. Non-metals are on the right.
- Metals: shiny, good conductors of heat and electricity, malleable, usually with 1 to 3 outer electrons
- Non-metals: dull, poor conductors, brittle when solid, many are gases, usually with 4 to 8 outer electrons
A zig-zag line separates the two. Sodium (Group 1) is a metal and chlorine (Group 7) is a non-metal.
Section 4
Metalloids
Metalloids are the elements along the zig-zag line between metals and non-metals, such as silicon and germanium. They have some properties of each. For example, silicon is shiny like a metal but brittle like a non-metal, and it conducts electricity only partly. This makes it a semiconductor, which is useful in computer chips.
Must know
- The table is in order of atomic number, in groups (columns) and periods (rows)
- Outer electrons = group number; occupied shells = period number
- Same group means the same outer electrons, so similar properties
- Metals on the left, non-metals on the right, metalloids on the boundary
- Metals are shiny, malleable conductors; non-metals are dull, brittle and poor conductors
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Organisation of the periodic table
- A teacher is explaining to her class how the elements are organised in the periodic table. The elements are laid out in rows and columns, and she wants the students to understand what decides where each element goes.Explain why elements in the same group have similar chemical properties.2 marks
- A technician has four unlabelled samples to sort. Sample W is a shiny solid that conducts electricity well and can be hammered into thin sheets. Sample X is a dull yellow solid that is brittle and does not conduct electricity. Sample Y is a shiny solid that is brittle and conducts electricity only poorly. Sample Z is a colourless gas at room temperature.Explain, using the information given, why sample X is classified as a non-metal.2 marks
- Two unknown elements, P and Q, have the electron arrangements 2,8,5 and 2,8,8,2 respectively. Students are given a periodic table and asked to work out the position of each element from its electron arrangement.State the atomic number, the group and the period of element P.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).