1. Chemistry Flashcards
What did the ancient Greeks do for the atomic theory? What was their evidence?
Atomic theory begun with Greek philosopher Aristotle, who stated that matter was indivisible.
However, another Greek philosopher, Democritus, disagreed. He stated in that everything could be broken down until it was just a single cell, which he named an ‘atom’. Invisible when singular, yet visible when grouped, atoms are indestructible and come in many different shapes and sizes.
The evidence for Democritus’ discovery was that in breaking down an object, the particles contained within them will continue to become smaller and smaller.
What did John Dalton do for the atomic theory? What was his evidence?
In the early 1800s - just 2000 years later - John Dalton was able to disprove Aristotle’s theory that matter was indivisible. Expanding on Democritus’ discovery, Dalton stated that matter is made up of tiny particles, called atoms, which cannot be divided or destroyed.
Dalton further stated that atoms of the same element will be the exact same and that atoms of different elements can combine to form compounds.
What did J.J. Thomson do for the atomic theory? What was his evidence?
By the late 1800s, atomic theory was beginning to gain some credibility. in amongst all this, J.J. Thomson would revolutionise the theory yet again with his discovery of the electron.
Thomson discovered the electron through utilisation of a ‘cathode ray tube’ (electron gun) and a magnet, Thomson discovered that the green beam the ray produced was made of negatively charged material. Upon redoing the experiment multiple times, Thomson concluded that the mass of one of the particles in the ray was 2000 times lighter than a hydrogen atom.
The gist of his discovery was that the lighter particle must have must have been from somewhere within the atom and that Dalton was incorrect for saying that atoms cannot be divided. Thomson deemed these negatively charged atoms as ‘electrons’. He said that electrons required something positive in order to be balanced out.
J.J. Thomson stated that his structure of the atom was like a ‘plum pudding’ model. The negatively charged ‘plums’ were surrounded by the positively charged ‘pudding’.
What did Ernest Rutherford do for the atomic theory? What was his evidence?
In the early 19th century, Ernest Rutherford, a student of J.J. Thomson redid some tests on Thomsons’ plum model, saying that atoms consisted of mostly empty space. Rutherford also discovered that Nucleus’ exist within an atom.
By shining a beam of positively charged particles (alpha particles) over a thin sheet of gold foil, Rutherford had expected all the particles to travel through the veil of gold if it were to appease Rutherford’s theory of the plum pudding model. To his surprise, some particles did travel through the gold veil whereas others did not, and were rather deflected.
Rutherford concluded that there must have been some positively-charged material within the gold sheet which reflected the positive charge within the atoms.
What did Niels Bohr contribute to the atomic theory? What was his evidence?
Niels Bohr worked with Ernest Rutherford on his research into the atom. Around 1922, Niels Bohr developed the now modern depiction of an atom, with the nucleus at the centre and orbiting electrons, which earned him a noble prize within the very same year.
What did James Chadwick contribute to the atomic theory? What was his evidence?
Another colleague of Ernest Rutherford. James Chadwick was the first man to discover the neutron.
What did Erwin Schroedinger contribute to atomic theory? What was his evidence?
Erwin Shroedinger used mathematical equations to describe the location and energy of an atom.
What is an atom?
The fundamental building block of matter and life. An atom is the smallest an element can go.
What is the modern atom shape?
A centered nucleus consisting of protons and neutrons surrounded by multiple electron shells.
What was J.J. Thomson’s outdated plum-pudding model?
J.J. Thomson’s plum pudding model stated that every neutron must be neutralised by a proton. His diagram shows the ‘plums’ as neutrons being neutralised by the ‘pudding’, a representation of protons.
What is the nucleus of an atom?
The nucleus of an atom is the dense, centre of an atom surrounded by electrons. The nucleus of an atom consists of protons and neutrons.
What are protons? How much charge is in a proton and how much do they weigh (atomic mass)?
Protons are located inside the nucleus.
- They are positive and have one unit of atomic mass.
- The atomic number is the number of protons (A) (and the atoms number in the periodic table).
What are neutrons? What is the formula for calculating Neutrons? How much charge is in a neutron and how much do they weigh (atomic mass)?
Neutrons are located inside the nucleus.
- They have no charge and have 1 unit of atomic mass.
- The mass number (A) is the number of protons + the number of neutrons.
- Number of Neutrons = A - Z.
What are isotypes? What are the properties of isotypes?
Isotypes:
- Have the same number of protons but different number of neutrons.
- Are the same element with the same chemical properties, but have different masses.
What are Electrons?
Electrons:
- Will equal Z for a neutral atom.
