Atoms, Isotopes and Atomic Structure

• What is an atom ?

  Smallest part of an element that can exist
• What does nucleus contains?

  Protons and Neutrons
• Why is the mass of an atom concentrated in nucleus?

  Nucleus contains the heaviest subatomic particles
• What is the electrical charge of a neutral atom?

  0
• What can atomic number be referred to?

  Number of protons
• Please provide the alternative name for mass number

  Nucleon number
• Is the number of proton equivalent to the number of electrons if the element is neutral?

  Yes
• How to find the nucleon number?

  Proton + Neutron
• What are isotopes?

  Atoms of the same element with the same number of protons but different number of neutrons
• What are the similar properties in isotopes?

  Chemical properties
• Why do isotopes shares the same chemical properties?

  Same electronic configurations
• What decides chemical properties?

  Number of electrons and arrangement of electrons
• What is the properties that are slightly different for isotopes?

  Physical properties
• Why do isotopes have different physical properties?

  Different number of neutrons
• What does physical properties depends on?

  Mass of the atom
• What are the important information to calculate $A_r$


  Mass of isotopes and percentage of abundance of each isotopes
• What did Democritus stated?

  Atoms are small, hard particles that were all made of the same material but were different sizes and shapes. Atoms were infinite in number, always moving and capable of joining together
• Dalton's Atomic Theory

  All matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties. Compound are formed by a combination of two or more different kind of atoms. A chemical reaction is a rearrangement of atoms. Atoms can neither created nor destroyed.
• Thomson's Atomic Theory

  Atom is not indivisible as it was of smaller pieces. Electrons and protons. An atom consists of a sphere of positively charge with negatively charged electron embedded in it. The positive and the negative charges in an atom are equal in magnitude, due to which an atom is electrically neutral. It has no overall negative and positive charge.
• Who invented the plum pudding model?

  Thomson
• Who discovered electrons?

  Thomson
• Rutherford's Atomic Theory

  Most mass of an atom is concentrated in the centre of the atom, in a nucleus. Atom mainly consist of empty spaces with nucleus in the centre and electrons orbiting in paths around the nucleus.
• Bohr's Atomic Theory

  Electron orbits the nucleus in fixed shells of specific energies. Orbit the nucleus without losing energy. Electrons with lower energy orbits closer to the nucleus while electrons with high energy will orbit further from nucleus.