Answer: Dalton’s model
Explanation:
The question is incomplete. But don't worry! The complete question is written below:
The model of the atom has changed as scientists have gathered new evidence. Four models of the atom are shown below, but one important model is missing.
Which atomic model is missing from this set (image attached)?
Bohr’s model
Dalton’s model
Rutherford’s model
Thomson’s model
Now, let's begin with the answer!:
In the attached image we can see four atomic models labeled with four letters:
W represents the <u>current and accepeted atomic model</u>: a nucleus with an electron cloud, where the orbit and position of the electrons around the nucleus is defined by specific regions (associated with specific energy levels) where there is a greater probability of finding the electron at any given moment. It is important to note this model was improved by the works in quantum physics done by Louis de Broglie and Erwin Schrodinger.
X represents<u> Rutherford's model</u> (This model was proposed after Thomson's model). Ernest Rutherford conducted a series of experiments in order to corroborate Thomson's atomic model. However the results of the experiment led him to find out there is a concentration of charge in the atom's core (which was later called nucleus) surrounded by electrons. This lead to a new atomic model, in which the atom has a positive charged nucleus surrounded by negative charged particles that move similar to the orbit of the planet around the Sun.
Y represents <u>Thomson's model</u>, also called the <em>plum pudding model</em>. This scientific found out that atoms contain small subatomic particles with a negative charge (later called electrons). However, taking into consideration that at that time there was still no evidence of the atom nucleus, Thomson thought the electrons were immersed in the atom of positive charge that counteracted the negative charge of the electrons. Just like the raisins embedded in a pudding or bread.
Z represents <u>Bohr's model</u>. This model was proposed by the danish physicist Niels Bohr after Rutherford's model. In fact, this model was Rutherford's model with the following addition: electrons orbit the nucleus (like planets around the sun) in specific orbits at different energy levels around the nucleus.
So, the only missing model is <u>Dalton's model</u>, which was the first atomic model:<u> the atom represented as a solid, indestructible and indivisible mass. </u>An idea that was already accepted by that time since the ancient Greeks.
