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Questions and Answers
Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or ______.
Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or ______.
electrons
Thomson proposed the ______ model of the atom, which had negatively-charged electrons embedded positively-charged 'soup'.
Thomson proposed the ______ model of the atom, which had negatively-charged electrons embedded positively-charged 'soup'.
plum pudding
Ernest Rutherford described the atom as a tiny, dense, positively charged core called a ______.
Ernest Rutherford described the atom as a tiny, dense, positively charged core called a ______.
nucleus
Electrons are found in ______ or orbitals that surround the nucleus of an atom.
Electrons are found in ______ or orbitals that surround the nucleus of an atom.
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Protons and neutrons are found in the ______ of an atom.
Protons and neutrons are found in the ______ of an atom.
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The organized array of all the chemical elements in order of increasing atomic number is called the ______.
The organized array of all the chemical elements in order of increasing atomic number is called the ______.
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Mendeleyev in the mid-19th century has been of inestimable value in the development of ______.
Mendeleyev in the mid-19th century has been of inestimable value in the development of ______.
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The number of protons determines the ______ of the element.
The number of protons determines the ______ of the element.
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The ______ Mass is a weighted average of all of the isotopes of that element.
The ______ Mass is a weighted average of all of the isotopes of that element.
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Atoms with the same number of protons but different numbers of ______ are called isotopes.
Atoms with the same number of protons but different numbers of ______ are called isotopes.
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The nuclear symbol is a type of shorthand notation that identifies the element and the ______ number of the element.
The nuclear symbol is a type of shorthand notation that identifies the element and the ______ number of the element.
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The ______ number is the sum of the number of nucleons (protons and neutrons) in the atomic nucleus.
The ______ number is the sum of the number of nucleons (protons and neutrons) in the atomic nucleus.
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Joseph John Thomson is known for his experiments with the ______
Joseph John Thomson is known for his experiments with the ______
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John Dalton's theory states that all matter is made of ______
John Dalton's theory states that all matter is made of ______
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According to Dalton, compounds are combinations of two or more different types of ______
According to Dalton, compounds are combinations of two or more different types of ______
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Democritus believed that atoms were uniform, solid, hard, incompressible, and ______
Democritus believed that atoms were uniform, solid, hard, incompressible, and ______
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John Dalton's theory states that all atoms of a given element are identical in ______ and properties
John Dalton's theory states that all atoms of a given element are identical in ______ and properties
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The Greek philosopher suggested the world was made of two things - empty space and ______
The Greek philosopher suggested the world was made of two things - empty space and ______
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Study Notes
Atomic Structure
- Understanding atomic structure helps us comprehend how atoms combine to form compounds, collide, and exhibit various properties.
Atomic Models
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Democritus' atomic model (460 BC): • Atoms are uniform, solid, hard, incompressible, and indestructible. • Atoms move in infinite numbers through empty space until stopped. • Differences in atomic shape and size determine the various properties of matter.
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John Dalton's atomic model (1804): • All matter is made of atoms, which are indivisible. • All atoms of a given element are identical in mass and properties. • Compounds are combinations of two or more different types of atoms.
Subatomic Particles
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J.J. Thomson's discovery (1856): • Cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles called electrons. • The plum pudding model of the atom, with negatively-charged electrons embedded in a positively-charged "soup."
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Ernest Rutherford's discovery (1871): • The atom consists of a tiny, dense, positively charged core called a nucleus, with nearly all the mass concentrated. • The nucleus is surrounded by light, negative constituents called electrons at some distance. • The atom is mostly empty space.
The Atom
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Electrons: • The smallest of the three particles that make up atoms. • Found in shells or orbitals that surround the nucleus. • Negative charges (-).
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Protons: • Found in the nucleus. • Positive charges (+).
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Neutrons: • Found in the nucleus. • No charge (neutral).
The Periodic Table of Elements
- The organized array of all chemical elements in order of increasing atomic number.
- The periodic law: elements in the same column (group) have similar properties.
Atomic Number and Mass
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Atomic Number: • The number of a chemical element in the periodic system. • The number of protons in the nucleus determines the identity of the element.
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Atomic Mass (Mass Number): • A weighted average of all the isotopes of an element. • The mass of each isotope is multiplied by its abundance.
Isotopes
- Atoms with the same number of protons but different numbers of neutrons.
- Share almost the same chemical properties but differ in mass and physical properties.
- Stable isotopes do not emit radiation, while unstable isotopes do emit radiation.
Nuclear Symbol Notation
- A shorthand notation that identifies the element (by symbol or atomic number) and the mass number of the element.
- The mass number is the sum of the number of nucleons (protons and neutrons) in the atomic nucleus.
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Description
Learn about the plum pudding model of the atom proposed by J.J. Thomson and Ernest Rutherford's description of the atom with a dense, positively charged nucleus. Explore the contrasting views of these scientists on the atomic structure.
