Photo AI
In 1804 the atomic theory of John Dalton was first published - VCE - SSCE Chemistry - Question 1 - 2006 - Paper 1
Question 1
In 1804 the atomic theory of John Dalton was first published. Two of the ideas expressed in his theory are listed below. How does our current understanding of atomic... show full transcript
Worked Solution & Example Answer:In 1804 the atomic theory of John Dalton was first published - VCE - SSCE Chemistry - Question 1 - 2006 - Paper 1
Step 1
i. All matter is composed of tiny, indivisible particles called atoms.
Answer
Our current understanding of atomic structure differs from Dalton's idea in that atoms are not indivisible; they can be divided into subatomic particles such as protons, neutrons, and electrons. Furthermore, the existence of composite particles and the processes of fission and fusion illustrate that atomic matter can be broken down more fundamentally than Dalton proposed.
Step 2
ii. Atoms of the same element are identical in every respect.
Answer
Modern atomic theory acknowledges that atoms of the same element can vary in mass due to the existence of isotopes. These isotopes have the same number of protons but different numbers of neutrons, leading to different mass numbers. Therefore, the assertion that all atoms of an element are identical is incomplete, as they can exhibit variations in their nuclear composition.
Step 3
b. i. How does this theory explain that the emission spectrum of hydrogen consists of a set number of discrete lines?
Answer
Bohr's theory explains the emission spectrum of hydrogen through the quantization of energy levels. When electrons transition between these fixed energy levels, they emit or absorb specific amounts of energy in the form of light. This energy corresponds to particular wavelengths of light, resulting in discrete spectral lines. The fixed orbits limit possible electron transitions, leading to the observed discrete emission spectrum.
Step 4
ii. State one way in which our present understanding of the electron structure of atoms in general differs from that proposed by Bohr for the hydrogen atom.
Answer
One significant difference is that our current understanding incorporates quantum mechanics, which describes electrons as existing in probabilistic orbitals rather than fixed orbits. Unlike Bohr’s model, which depicted electrons as moving in definite paths, the modern quantum mechanical model represents electron locations as cloud-like distributions, where it is only possible to define the probability of finding an electron in a particular region.