Question

4.3 atomic structure

1. experiments by j.j. thomson showed that atoms have

sketch the cathode ray tube experiment and label its components. (late 1890s)
sketch the
pudding model and label its components.

1. rutherfords experiment (1911) discovered the nuclear atom

he used
particles and thin gold foil to demonstrate:
atoms have a dense center of positive charge called the
the nucleus, which is at the center of the atom, consists of (positively charged) and (uncharged).
electrons move around the nucleus. sketch rutherfords model.

1. introduction to the modern concept of atomic structure

particle	relative mass	relative charge
proton	+1
	1839	none

1. neils bohr (1913) discovered that electrons in the atom can only occupy certain energy levels around the nucleus. sketch bohrs model.
2. isotopes are atoms with the same number of protons but different numbers of neutrons.

a particular isotope is represented by the symbol $_{z}^{a}x$
where
a = number (sum of protons and neutrons)
z = atomic number (number of )
x =

Explanation:

Step1: Recall J.J. Thomson's discovery

Experiments by J.J. Thomson showed that atoms have electrons.

Step2: Recall components of cathode - ray tube

The cathode - ray tube has a cathode (negative electrode), anode (positive electrode), and a fluorescent screen.

Step3: Recall Thomson's model

Thomson's model is called the plum - pudding model. It consists of a uniform positive charge with electrons embedded in it.

Step4: Recall Rutherford's experiment

Rutherford used alpha ($\alpha$) particles and thin gold foil. He discovered that atoms have a dense center of positive charge called the nucleus. The nucleus consists of protons (positively charged) and neutrons (uncharged).

Step5: Recall atomic particle properties

The relative charge of an electron is - 1. The relative mass of a proton is 1836. The particle with a relative mass of 1839 and no charge is a neutron.

Step6: Recall isotope notation

In the isotope notation $^{A}_{Z}X$, A is the mass number (sum of protons and neutrons), Z is the atomic number (number of protons), and X is the chemical symbol of the element.

Answer:

1. electrons; Cathode - ray tube components: cathode, anode, fluorescent screen; Plum - pudding model components: uniform positive charge, electrons
2. alpha; nucleus; protons; neutrons
3. - 1; 1836; neutron
4. Sketch of Bohr's model: Nucleus at the center with electrons in circular orbits at specific energy levels around it
5. mass; protons; chemical symbol of the element