Atomic structure presentation

Atomic structure of an atom and it's models

1. ATOMIC STRUCTURE

2. What is an Atom? Atom comes from the Greek word atomos , which means something invisible and cannot be cut or divided. It was coined by Democritus in 450 BC. But in 19 th and the 20 th centuries, physicists discovered that there are still subatomic particles within an atom. And therefore the name is not appropriate anymore.

3. Atomic Structure + + Neutrons Protons Nucleus Electrons _ _ Atoms are made of smaller particles, called electrons, protons, and neutrons. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Electrons and protons have a property called electric charge, which affects the way they interact with each other and with other electrically charged particles

4. + Neutrons _ _ Is a subatomic particle forming part of the nucleus of an atom. It has no charge. It is equal in mass to a proton or it weighs 1 amu . Protons Is a positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element. It weighs 1 amu . + +

5. + + Electrons _ It contribute greatly to the atom’s charge, as each electron has a negative charge equal to the positive charge of a proton. It is located in shells that surround an atom’s nucleus. _ Nucleus Is the central part of an atom, which is composed of protons and neutrons and contains most of an atom’s mass. + +

6. Atomic History Democritus (460 BC – 37 BC) Democritus’ Atomic Model Greek philosopher the first to create an atomic model. According to him, matter can be cut down into smaller and smaller pieces, until it reaches the tiniest piece called the atom .

7. John Dalton (1766 - 1844) Born in Cumberland, England His Theory: That atoms are indivisible spheres that are neither created nor destroyed. Atoms of the same element are identical. Atoms of different elements have different masses. Atoms can be rearranged and combined in fixed ratios to form compounds Bowling Ball Atomic Model

8. Joseph John Thomson (1856 – 1940) Born in Cheetham Hill, England Discovered electron in 1897. Used a cathode ray tube to show the atoms of any element emit particles with a negative charge. Plum Pudding Atomic Model _ _ _ _ _ _ _ _ + + + + + + + Sea of positive charge electron Discovered that the electrons were placed randomly in a positive matrix. Came up with the plum pudding model

9. Ernest Rutherford (1871 – 1937) Born in Nelson, New Zealand Father of nuclear physics Discovered the nucleus in 1911 when he conducted the Gold Foil Experiment with the help of Hans Geiger and Ernest Marsden. His Theory: All the positive charges were concentrated in the nucleus. The negatively charged electrons revolved around the nucleus. Came up with the planetary model or nuclear model of atom.

10. Niels Bohr (1885 – 1962) Born in Copenhagen, Denmark His Theory: An atom is made up of protons, which are concentrated in the nucleus Electrons orbit around the nucleus along concentric orbital paths. Electrons have quantized energy levels and they can transfer from one orbit to another.

11. James Chadwick (1891-1974) English Physicist Discovered neutron in 1932 Discovery of neutron (mass = 1.67493 x 10 -24 g) explained the mass problem of many atoms. Nobel Prize in Physics 1935 His Theory: Neutrons have no electrical charge. Neutrons have a mass nearly equal to the mass of a proton. Unit of measurement for subatomic particles is the atomic mass unit ( amu ). electron neutron proton nucleus

12. Isotopes Atoms of the same element having different mass numbers and are therefore found in the same position in the periodic table. Are different versions of an element. Are radioactive when they emit radiation (radioisotopes) Types of Radiation Particle radiation - refers to alpha and beta particles, protons, and neutrons given off by isotopes. Electromagnetic radiation - refers to gamma rays and X-rays emitted by isotopes.

13. Electron Orbitals Is a probability function that describes where electrons may be found. Are not orbits rather they are electron density clouds which describe the highest probability distribution of electrons. Four types of orbitals : s, p, d, and f s Is a sphere, The simplest orbital and can hold up only two electrons p The subshell consists of six three dimensional lobes and can hold up to six electrons. d can hold up to ten electrons. Is made of five subshells which can hold two electrons each. f made up of seven complex orbitals , can hold fourteen electrons.

14. Electron Configuration The distribution of electrons among orbitals in an atom. An atom can be configured without drawing or illustrating any of the s, p, d, and f orbitals . TWO WAYS OF DETERMINING HOW ELECTRONS ARE ARRANGED IN AN ATOM. 1. Periodic Table 2. Diagonal Rule

15. The Periodic Table of Elements Elements within a group have similar physical and chemical properties All have the same number of electrons in their outermost or valence shells Example Na (2,8,1) and K (2,8,8,1) are both in Group 1

16. End THANK YOU!