Science M.C.Q. [1 M]

According to Thomson’ model of the atom, an atom consists of a sphere of positively charge with negatively charged electrons embedded in it. These negative and positive charges in an atom are equal in magnitude, due to which an atom is electrically neutral.

Rutherford suggested highly charged centrally concentrated small volume called as atomic mass and this region is known as nucleus of atom and gave the nuclear model of atom.

Thomson's model of atom states that:
An atom consists of a positively charged sphere with electrons embedded in it.
Total positive and negative charges in the atom are equal in magnitude. So, atom is electrically neutral.

Atom is made of particles called electrons, neutrons, and protons.
Electrons have negligible mass and hence do not contribute much to the mass of an atom.
Protons and neutrons contribute to the mass of an atom and are present in a small region called the nucleus.

Valence electrons of an atom are those electrons that are involved in chemical bonding. When forming chemical bonds, atoms may lose, gain, or share valence electrons. An element's chemical properties, including its reactivity, depend on how easily its atoms gain, lose, or share valence electrons.

When alpha particles are sent through a thin metal foil, most of them go straight through the foil because most of the space inside the atom is empty.

Bohr's atomic model can explain the spectrum of atoms or ions which are uni-electron. It cannot explain the spectrum of the multi-electron system.

Atomic mass number is sum of number of protons and neutrons in an atom of the element.

Thomson proposed that the nucleus of an atom contains only nucleons.

The particles present in the nucleus of an atom are the proton and the neutron.
Electrons are revolving around the nucleus in circular orbits.

Hydrogen atom contains one proton in the nucleus and one electron outside the nucleus.
The space between a proton and electron in hydrogen atom is empty.

The observation that most alpha particles passed straight through the gold foil led Rutherford to conclude that the positive charge in an atom is concentrated in a very small area that is called nucleus.
Atoms have mostly empty space.
Electrons, which are negatively charged, are distributed throughout this space but take up a very small part of it.

In an atom, the number of electrons is equal to number of protons, which in turn is equal to the atomic number of the element. Also, the sum of number of protons and neutrons represents the mass number of the element.

Isotopes are the atoms of the same element with the same atomic number but different mass numbers. It means that they have the same number of protons and electrons but different number of neutrons.

Alpha particles are positively charged and were deflected by the nucleus. This showed that nucleus is positively charged. Rutherford also postulated that electrons are arranged in an atom around the nucleus, in the same way as planets are arranged around the Sun in the Milky Way.

An atom consists of a positively charged, dense and very small nucleus which have all the protons and neutrons. Positive charge is due to protons, as neutrons have no charge. Most of the space is empty because most of the alpha particles pass straight through the gold foil without any deflection.
Electrons have negative charge, it was explained by Thomson. The existance of neutron was discovered by Chadwick.

Two nuclides are isotones if they have the very same neutron number but different proton number.

It was observed in Rutherford's experiment of gold foil that very few α particles were deflected back by large angles.
The deflection of only a very few α particles helped him to conclude that the nucleus occupies very little space in an atom.
He also concluded that the nucleus would be dense to deflect the α particles by large-angle.

The atom consists of a tiny nucleus surrounded by moving electrons.
The nucleus contains protons, which have a positive charge equal in magnitude to the electron's negative charge.
The nucleus may also contain neutrons, which have virtually the same mass but no charge.

The nucleus of a hydrogen atom is called a proton as it has only one proton in it.

Malleability is a property of metals which can be beaten into sheets.
For his experiment Rutherford needed a very thin sheet of metal and hence he selected gold metal which could be beaten into very thin sheet.

The electrons revolve around the nucleus in circular paths was first proposed by Rutherford, not by Thomson.