![]() ![]() Valency can be considered as number of Valence electrons but in some cases it may have different meaning. The combining capacity of the atoms to form molecules either with same or different elements is defined as Valency. Elements with same number of valence electrons have similar chemical properties whereas the elements with different valence electrons have different chemical properties.These elements gain electrons and forms a negatively charged ion called anion.Elements having valence electrons 4, 5, 6 or 7 are called as Non-metals.These elements lose electrons easily and form a positively charged ion called cation.Elements having valence electrons 1, 2 or 3 are called metals.Įxception: Hydrogen has 1 valence electron but it is not consider as a metal.Since they are ones that are participate in a chemical reaction. The chemical properties of an atom are dependent on these valence electrons. Hence the number of valence electrons present in sodium is 1. In sodium 3 rd shell is the outermost shell (valence shell). The electrons, which are present in the outermost shell of an atom are called valence electrons.Įlectronic configuration of sodium is 2, 8, 1 Now try to write the electronic configuration of Note the changes in the electronic configuration of Sc, V, Fe. Similarly the electronic configuration of other atoms are : Element ∴ Electronic configuration of sodium atom = 2, 8, 1 The electronic configuration of sodium: 1s 2, 2s 2, 2p 6, 3s 1 can also be written as 2, 8, 1 (indicating 1st shell has 2 electrons, 2nd shell has 8 electrons, 3rd shell has 1 electron). Fill these electrons in the sequence till all electrons are not exhausted remember sub-shell can accommodate maximum number of electrons as s sub-shell = 2 p sub-shell =6, d sub-shell = 10 Check how many electrons are present in the atomģ. Now Its electronic configuration is 1s 2, 2s 2, 2p 6, 3s 1 Note: you can write electronic configuration easily, follow steps :ġ. The nucleus of sodium has 11 protons and 12 neutrons and it is surrounded by 11 electrons. Sodium has atomic number 11 and mass number 23. Electrons are filled up in an atom from Lower Energy Level to Higher Energy Level. “f” sub shell can hold a maximum of 14 electrons.Īrrangements of Shell and Sub – Shells : Shell Nameģ. “d” sub shell can hold a maximum of 10 electrons. “p” sub shell can hold a maximum of 6 electrons. “s” sub shell can hold a maximum of 2 electrons. Types of Sub Shell : Sub shells are s, p, d and f types.Įvery sub-shell can accommodate a fixed number of electrons. Electrons are present in these sub shells which constitute a Shell. After a series of experiments and a detailed study by scientists like Louis de Broglie, Schrödinger, Somerfield and others proved that shells or energy levels have Sub Shells within them. The maximum number of electrons that can be accommodated in any energy level of the atom is given by a formula 2n 2 where n is the number of that Orbit number/ Shell Number / Energy level.Ģ.Rules for accommodating electrons in various shells (Bohr-Bury Rules) If Bohr’s Model is considered to be valid Shells and Orbits are similar for indication purpose. Shell more correctly indicates a Sphere (a three dimensional object) while Orbits are Circular paths (A two dimensional object). Here for simplification, Students are advised to consider the sense same. Note: Shell and Orbits are not identical They are different ideas. These orbits or Shells are represented by the letters K, L, M, N,… or the numbers n = 1, 2, 3, 4,5.…. The arrangement of electrons in the shells is known as electronic configuration.Įlectrons are present in fixed energy levels called Shells. Number of Neutrons = Mass number – Atomic number = 40-18 = 22 In an atom number of electrons = Number of protons = 18 Find out the number of protons, number of electrons and number of neutrons present in the atom X? Question: An atom X has mass number 40 and atomic number 18. Mass number = Number of Protons + Number of NeutronsĪtomic number Element Mass number = Z X AĮxample: Sodium atom has notation as 11 Na 23. It is also referred as Atomic Mass.Įxample: Mass number of Nitrogen atom is 14 then it contains 7 protons and 7 neutrons. The mass number (A) is defined as the sum of the number of protons and neutrons present in the nucleus of an atom. Since for a neutral atom, the number of electrons is equal to number of protons, so Atomic Number is also equal to the number of electrons in neutral the atom.Ītomic number = Number of protons = Number of Electrons (for neutral atom)Įxample: The atomic number of Iron (Fe) is 26 Fe atom contains 26 protons and 26 electrons. Atomic number (z) is the number of protons in an atom. ![]()
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