- Information
- AI Chat
Chem historyoftheatomworksheet and video questions
Forensic Science (CHEM1118)
Fairleigh Dickinson University
Related Studylists
yPreview text
Name: ___________________________________ Per: ______ Date: ___________ History of the Atom Video Questions Video: The 2,400 year search for the atom youtube/watch?v=xazQRcSCRaY Democritus – (460-370 BCE) 1. 1st to propose that matter is made of tiny particles surrounded by empty space. 2. He called these particles Atomos. Aristotle_______________disagreed and said that matter was composed of 4 elements: earth, wind, water, and fire. By 1932, scientists had discovered that the nucleus of an atom contains two types of particles: protons, which have a positive charge, and neutrons, which are neutral (have no charge). Both of these particles have about the same mass, which is much larger than the mass of an electron. Since the masses are so tiny, we use usually talk about their masses relative to each other. Since the proton and neutron have approximately the same masses, we say their mass is 1, and the mass of the electron is so small in comparison, we say it is 0. 3. 4. Atoms were largely forgotten until Dalton_______________’s theory in the 19th century. Video: Chem & Physics: History of the atom youtube/watch?v=-4Us5PTb4J Dalton – (1803) 1. Everything is composed of atoms___________and helped to explain what occurred in chemical reactions. 2. Different elements____________________always combined to form chemical compounds_______________in amounts that were simple, whole number ratios_. 3. Each _element__ had its own unique type of atom with its own characteristic weight. 4. Atoms were solid and small_________. 5. This model of the atom lasted almost ___ 100 ____years. 6. The discovery of subatomic particles meant Dalton’s model needed some work.
Thomson – (1897) 1. Thomson was the 1st to discover a subatomic particle – the electron. 2. His experiments used cathode__ rays. 3. Thomson used electrically charged___________ plates to deflect cathode rays and estimate the mass. 4. He showed that cathode rays must be made up of negatively_____ charged particles that were over ___ 1000 _____ times____ smaller than the lightest atom (Hydrogen). 5. Thomson’s model is known as the plum pudding__ model. 6. Draw a picture of Thomson’s model.
Rutherford – (1909) 1. Alpha particles are a type of positively____ charged radiation. 2. When shot at a piece of gold foil, most alpha particles pass straight__________ through. But occasionally, an alpha particle would be violently. deflected__ back, as if it has hit something massive. 3. The Gold Foil experiment led to the discovery of the nucleus_, which is the center of the atom, where most of the mass of an atom is concentrated. 4. The core of an atom is _positively_________ charged. 5. Draw a picture of the Rutherford model of the atom.
- What was the problem with Rutherford’s model of the atom? There was nothing to stop the positive nucleus.
Bohr – (1913) 1. Draw a picture of Bohr’s model of the atom.
Bohr proposed that electrons are found in circular Orbits________ around the nucleus.
Bohr’s model is known as the Planetary________ model of the atom.
According to Bohr’s model, electrons are found in fixed energy_______ levels.
The path closest to the nucleus has the Lowest________ energy. The energy is generally higher_______ as electrons are farther away from the nucleus.
According to Dalton, what are elements made of? Atoms_______ Can they be divided? NO______
An atom of hydrogen and an atom of carbon are different_______________.
Two atoms of hydrogen are the same__________.
What are compounds made of? Atoms of different elements_______________
How do elements combine? number ratios_________
The ratio of atoms in H 2 O is: a) 1:1 b) 2:1 c) 1:
Draw a picture of Dalton’s atom.
J. J. Thomson (Late 1800s): J. J. Thomson was an English scientist. He was experimenting with gas discharge tubes when he noticed a movement in the tube. He called the movement cathode rays. The rays moved from the negative end of the tube to the positive end. When he held a negative metal plate near the cathode ray, the ray was deflected away. No matter which gas he put into the tube, he always made the same observations. He realized that the rays were made of negatively charged particles – electrons. His plum pudding model describes the atom as a sphere of positively charged “pudding”, with negative electrons evenly distributed throughout, like plums in the pudding.
- Why are cathode rays deflected away from a negatively charged metal plate? Charges repel each other and cathode said it was negative.
- Why do cathode rays move from the negative end of the tube to the positive end? Opposites attract
- What are cathode rays made of? Electrons. What charge do they have? Negative
- Why did Thomson see cathode rays with every element tested? Every element has electrons in its atom
- Draw a picture of Thomson’s atom.
Ernest Rutherford (1871 – 1937): Ernest Rutherford conducted a famous experiment called the gold foil experiment. He used a thin sheet of gold foil. He also used special equipment to shoot alpha particles (positively charged particles) at the gold foil. Most particles passed straight through the foil like the foil was not there. Some particles went straight back or were deflected as if they had hit something. The experiment shows: Atoms are made of a small positive nucleus; positive nucleus repels positive alpha particles Atoms are mostly empty space
What is the charge of an alpha particle? Positive_____________________
Why is Rutherford’s experiment called the gold foil experiment? Because he shot alpha particles at a thin sheet
How did he know that an atom was mostly empty space? Moat particles passed straight through the gold atoms
Why did Rutherford conclude that atoms contain a nucleus? Some particles were deflected by the gold atoms
How did he know that the nucleus was positively charged? It repelled the positive alpha particles
Rutherford’s atom is called the nuclear atomic model. Draw a picture of it.
The proton and the neutron: By 1932, scientists had discovered that the nucleus of an atom contains two types of particles: protons, which have a positive charge, and neutrons, which are neutral (have no charge). Both of these particles have about the same mass, which is much larger than the mass of an electron. Since the masses are so tiny, we use usually talk about their masses relative to each other. Since the proton and neutron have approximately the same masses, we say their mass is 1, and the mass of the electron is so small in comparison, we say it is 0. Complete the chart below.
Subatomic Particle Relative Mass Charge Location Proton Neutron electron
Draw a picture of an atom, showing the location of the protons, neutrons, and electrons. Make sure the parts of the atom are labeled.
Chem historyoftheatomworksheet and video questions
Course: Forensic Science (CHEM1118)
University: Fairleigh Dickinson University
