AL- Atomic Theory

Which one of the following is not one of the postulates of Dalton's atomic theory?

• Atoms are composed of protons, neutrons, and electrons.

• All atoms of a given element are identical; the atoms of different elements are different and have different properties.

• Atoms of an element are not changed into different types of atoms by chemical reactions: atoms are neither created nor destroyed in chemical reactions.

• Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.

• Each element is composed of extremely small particles called atoms.

Which of the following is/are postulates of Dalton’s atomic theory?

1. 1. Atoms combine in fixed ratios of whole numbers.

2. 2. Atoms of each element have different properties.

3. 3. Elements occur as solids, liquids, or gases.

• 1 only

• 2 only

• 3 only

• 1 and 2

• 1, 2, and 3

Consider the following selected postulates of Dalton's atomic theory: (i) Each element is composed of extremely small particles called atoms. (ii) Atoms are indivisible. (iii) Atoms of a given element are identical. (iv) Atoms of different elements are different and have different properties. Which of the postulates is(are) no longer valid?

• (i) and (ii)

• (ii) only

• (ii) and (iii)

• (iii) only

• (iii) and (iv)

In the absence of magnetic or electric fields, cathode rays __________.

• do not exist

• travel in straight lines

• cannot be detected

• become positively charged

• bend toward a light source

Cathode rays are deflected away from a negatively charged plate because __________.

• they are not particles

• they are positively charged particles

• they are neutral particles

• they are negatively charged particles

• they are emitted by all matter

Cathode rays are

• anions.

• protons.

• cations.

• positrons.

• electrons.

Cathode rays are __________.

• alpha rays

• x-rays

• electrons

• protons

• atoms

Who discovered the electron?

• Bohr

• de Broglie

• Rutherford

• Heisenberg

• Thomson

Which one of the following is not true concerning cathode rays?

• They originate from the negative electrode.

• They travel in straight lines in the absence of electric or magnetic fields.

• They impart a negative charge to metals exposed to them.

• They are made up of electrons.

• The characteristics of cathode rays depend on the material from which they are emitted.

In a cathode ray tube

• electrons pass from the anode to the cathode.

• electrons pass from the cathode to the anode.

• protons pass from the anode to the cathode.

• protons pass from the cathode to the anode.