Revisions to Dalton’s Theory
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What was Dalton's theory on the structure of matter?
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Proposed that all matter is made up of individual particles called atoms, which cannot be divided.
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Main points (4) of Dalton's theory explained data of many experiements and became widely accepted Over time, some proved incorrect, but scientists revised the theory based on new discoveries.
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1, All elements are composed of atoms. 2. All atoms of the same element have the same mass, and atoms of different elements have different masses. 3. Compounds contain atoms of more than one element. 4. In a particular compound, atoms of different elements always combine the same way.
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JJ Thompson's experiments proved Plum Pudding Model
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that atoms are made of even tinier particles and revised Dalton's theory (with round balls) to include atoms had particles. to account for positives and negative particles balancing out. Could be Choc Chip Ice cream (chips to ice cream ratio balancing out positives and negatives.
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Rutherford's Model
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based on his gold foil experiment is ALL OF AN ATOMS POSITIVE CHARGES ARE CONCENTRATED IN ONE PLACE WHICH HE NAMED THE NUCLEUS.
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What are three subatomic particles?
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Protons, electrons, and neutrons. Rutherford had found 2 of three
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What properties can be used to compare protons, electrons, and neutrons?
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mass, charge and position in the atom.
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How are atoms of one element different from atoms of others?
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Atoms of different elements have different numbers of protons. This is the basis of the Atomic Number system
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What is the difference between 2 isotopes of the same element?
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Isotopes of the same element have the same atomic number but different mass numbers of neutrons.
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Proton (p+) Rutherford Isolated
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Positively charged subatomic particle found in the nucleus. Elements can have 1+ to 100+ charges.
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Electron (e-) Thompson isolated but did not name
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is a negatively charged subatomic particle that is found outside the space of the nucleus. (from electros, greek for amber) NOTED 1-
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Dalton predicted atoms of any element were different with subatomic particles identified, now scientist could compare
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Scientists cannot see subatomic particles but know of them through their behavior.
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Neutron (n) Chadwick found its location
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is a neutral subatomic particle that is found in the nucleus of an atom.
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atomic number
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the atom of any element always has the same number of protons , Atomic number is the number of protons for each element. They also have the same number of electrons to balance the positive and negative charges.
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mass number
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is the sum of protons and neutrons in the nucleus of the atom. Mass number - atomic number = no. of neutrons.
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In Dalton's theory, all atoms were identical. BUT
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While every atom has the same number of protons and electrons, it DOES NOT HAVE SAME number of neutrons.
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isotopes
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are atoms of the same element that have different numbers of neutrons and different mass numbers.
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What model do scientists use to describe how electrons behave in atoms?
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The electron cloud. It is used to describe the possible locations of the electrons around the nucleus.
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Hydrogen isotopes are an exception to the rule
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Most isotopes it hard to notice any chemical or physical property differences. Hydrogen -1 makes water, Hydrogen -2 makes heavy water which has different physical properties (melting and boiling point, and density)
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What can happen to electrons when atoms gain or lose energy?
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Electrons can move energy levels whenever an atom gains or loses energy. The size of the jump between energy levels is determined by the amount of energy gained or lost. EX: Colors of fireworks, light, energy is released as visible light. Because no two elements are the same they emit different colors of light.
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electron cloud
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is a visual model of the most likely locations for electrons in an atom. Cloud is denser closer the electrons are to the nucleus. It is a good approximation of how electrons behave in their orbitals.
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What is the most stable configuration of electrons in an atom?
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The ground state, when all electrons are at their lowest possible energy levels.
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energy levels
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describes possible energies that electrons in an atom can have (because they can change). No two elements have the same energy level.
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orbital
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the region of space around the nucleus where an electron is likely to be found.
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electron configuration
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is the arrangement of electrons in the orbitals of the atoms.
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ground state
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when all the electrons in an atom are at their lowest possible energy states, the atom is said to be in GROUND STATE (most stable)
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excited state
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when enough energy is gained that one or more of the electrons can move to an orbital with higher energy, eventually the atoms losses this source of energy and the atom returns to the ground state. Some gases, like helium, emit the light you see in "neon" lights when they return from excited states to ground state. I
