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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
Current understanding has evolved to recognize that atoms are not indivisible; they can be broken down into smaller particles called subatomic particles, including protons, neutrons, and electrons. Moreover, atoms can undergo nuclear reactions, such as fission or fusion, which further illustrates their divisibility.
Step 2
ii. Atoms of the same element are identical in every respect.
Answer
Today, we understand that while all atoms of a given element share the same number of protons, they can differ in the number of neutrons, leading to the existence of isotopes. This variation means that not all atoms of an element are identical in terms of mass and some physical properties.
Step 3
How does this theory explain that the emission spectrum of hydrogen consists of a set number of discrete lines?
Answer
Bohr's theory suggests that electrons occupy specific energy levels or orbits around the nucleus. When an electron moves from a higher energy orbit to a lower one, it emits a photon of light with a specific wavelength. Since only certain energy levels are allowed, the emitted light appears as a series of discrete lines in the spectrum, corresponding to the energy differences between these orbits.
Step 4
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
Unlike Bohr's model, which depicted electrons in fixed orbits, current quantum mechanical models illustrate that electrons exist in orbitals, which are probability distributions rather than defined paths. This approach accounts for the behavior of electrons more accurately, reflecting their wave-particle duality.