Atomic Structure Part 2

Recap Atom is a particle which is electrically neutral No. of protons = No. of electrons An atom consists of 3 subatomic particles: 1) Protons 2) Neutrons 3) Electrons

Recap + Structure of an atom Relative charges and approximate relative masses of protons, neutrons and electrons + Electrons Nucleus Protons and Neutrons

Particle Charge Relative Mass Remarks Proton +1 1 Mass is the same as that of a hydrogen atom Found in the nucleus of the atom Neutron Electron -1 1/1836 One hydrogen atom weighs as much as 1836 electrons Found around the nucleus.

Recap Symbol of an atom Chemical Symbol Nucleon Number Proton Number

Recap Proton number (atomic number) The number of protons in an atom For an atom, no. of protons = no. electrons

Recap Nucleon number (mass number) = no. of protons + no. neutrons No. of Neutrons = Nucleon number – Proton number

Overview of topic Atomic Structure Ions Electronic Structure and the Periodic Table Structure of Atoms Atomic Structure Electronic Arrangement Isotopes

Today’s Menu What are isotopes Electrons arrangement in atoms Electronic structure Outermost electrons The Periodic table

What are isotopes?

What are isotopes Isotopes: Atoms of the same element having the same number of protons but different number of neutrons

What are isotopes Isotopes: Same number of protons (atomic number) Different number of neutrons Different number nucleon number Same number of electrons

Examples of isotopes Three isotopes of hydrogen 1) Hydrogen Number of proton: 1 Number of neutrons: 0 Nucleon number: 1 Number of electron: 1 Hydrogen-1

Examples of isotopes Three isotopes of hydrogen 2) Deuterium Number of proton: 1 Number of neutrons: 1 Nucleon number: 2 Number of electron: 1 Hydrogen-2

Examples of isotopes Three isotopes of hydrogen 3) Tritium Number of proton: 1 Number of neutrons: 2 Nucleon number: 3 Number of electron: 1 Hydrogen-3

Examples of isotopes Two isotopes of Chlorine Number of proton: 17 Number of neutrons: 18 Nucleon number: 35 Number of electron: 17 Number of proton: 17 Number of neutrons: 20 Nucleon number: 37 Number of electron: 17 Chlorine-35 Chlorine-37

What are isotopes Isotopes Number of Protons Neutrons Electrons 1 2

What are isotopes Isotopes: All isotopes of the same element have the same chemical properties but small differences in physical properties There are two types of isotopes (i) Radioactive (ii) Non-radioactive

Why does chlorine has a nucleon number of 35.5

Why does chlorine has a nucleon number of 35.5 In the periodic table, chlorine is denoted as

Why does chlorine has a nucleon number of 35.5 75% of all chlorine atoms have a mass of 35 25% of all chlorine atoms have a mass of 37 Average mass of one chlorine atom = = 35.5

Practice Time Part 3 Worksheet 2

Electrons Arrangement In Atoms

Electrons Arrangement in Atoms Electrons move around the nucleus of the atom The electrons are held in shells since it is of opposite charge The attractive force between the positive charge on the nucleus and the negative charge on the electrons is called electrostatic force.

Electronic Structure

Electronic Structure The way the electrons are arranged is called its electronic structure Electrons are arranged in shells which are numbered from the nucleus onwards Each shell is capable of holding up to a certain number of electrons

Maximum no. of electrons (for atoms with proton number 20) Electronic Structure Electrons are arranged in shells which are numbered: 1, 2, 3, 4 from the nucleus onwards Shell no. Maximum no. of electrons Name 1 2 Duplet 8 Octet 3 (for atoms with proton number 20)

Electronic Structure Nucleus 1st shell 2 electrons 2nd shell 3rd shell 8 electrons (proton number 20)

Electronic Structure To find the electronic configuration of an atom, we should Fill the electrons into the shell nearest to the nucleus first. This shell can take a maximum of 2 electrons Once this shell is filled, the electrons go to the next available shell which has a maximum capacity of 8 electrons, and so on

Electronic Structure Na Sodium, Electronic Configuration 2, 8, 1 1st shell Na 2nd shell 3rd shell

Electronic Structure C Carbon, Electronic Configuration 2, 4 1st shell 2nd shell

Electronic Structure Its important to know the electronic structure and electronic configuration of the first 20 elements of the Periodic Table

Summary

Summary 1) Isotopes are atoms of the same element having the same number of protons but different number of neutrons 2) Electrostatic force is the force between the positive charge on the nucleus and the negative charge on the electrons.

Maximum no. of electrons (for atoms with proton number 20) Summary Electrons are arranged in shells which are numbered: 1, 2, 3, 4 from the nucleus onwards Shell no. Maximum no. of electrons Name 1 2 Duplet 8 Octet 3 (for atoms with proton number 20)

Summary To find the electronic configuration of an atom, we should Fill the electrons into the shell nearest to the nucleus first. This shell can take a maximum of 2 electrons Once this shell is filled, the electrons go to the next available shell which has a maximum capacity of 8 electrons, and so on

Any Questions

Practice Time Part 3 Worksheet 2