Chapter 1- Voltage, Current and Resistance Flashcards
What is an atom
• Smallest particle of an element that retains its characteristics (Examples : Hydrogen, Oxygen, Carbon),and is characterized by a sharing of the chemical properties of the element and a nucleus with neutrons, protons and electrons.
What gives the atomic number of an element
- The number of protons gives the atomic number of an element.
View the periodic table here
Give the charge for the protons, neutrons and electrons of an atom
- Protons are positively charged particles
- Neutrons are uncharged particles
- Electrons are negatively charged particles
In its normal/neutral state, what does an atom have?
In its normal or neutral state, an atom has an equal number of protons and electrons.
What does each of the known elements have
• Each of the known elements has a unique atom structure and a unique atomic number
In the periodic table, atoms are arranged according to what?
In the periodic table, atoms are arranged according to their atomic number
The positive charge of a proton is equal to what? Why?
• The positive charge of a proton is equal and opposite to the one of an electron, because positive charge cancels the negative charge, therefore, the atom has a net charge of zero
What is electrical charge symbolised by? Why?
• Electrical charge is symbolised by Q, because:
Q is charge in coulombs (C)
What is static electricity
Static electricity is the presence of a net positive or negative charge in a material
What number determines the characteristics of the element?
The atomic number determines the characteristics of the element
What are the same in all elements, but their numbers differ?
Smaller particles like electrons or protons
Each atom of the known 109 elements have a unique number of what?
Each atom of the known 109 elements has a unique number of protons
What is referred to as ‘‘atomic number’’, that all 109 elements have a unique number of?
Protons
Elements in the periodic table are arranged according to what?
their atomic number
What number determines the characteristics of an element?
The atomic number
In an atom, what forms the nucleus?
Neutrons and Protons
What orbits the nucleus in an atom?
Electrons orbit the nucleus in an atom.
What is the charge of one electron ( or one proton ) in an atom?
1.6x10-19 C (C stands for Coulomb)
What does C stand for?
C stands for Coulomb
In its neutral state (without external forces applied), the atom has the same amount of what?
positive and negative charges (i.e the same number of protons and electrons).
What makes the atom neutral
Positive and negative charges cancel each other making the atom neutral.
Electrons orbit the nucleus at what distance from the centre
a discrete ( synonym - distinct ) distance
In the case of electrons, the closer from the nucleus the more what?
The closer from the nucleus the more tightly bound to it and the less amount of spare energy.
Electrons orbiting at the same distance from the nucleus have the same what?
Electrons orbiting at the same distance from the nucleus have the same energy level.
Electrons are grouped in energy bands known as ______. Why?
Electrons are grouped in energy bands known as shells, because electrons orbiting at the same distance from the nucleus have the same energy level
Regarding Electrons, each shell has a what?
Each shell has a fixed number of electrons given by 2N^2 (N being the shell number, starting at 1 for the closest shell to the nucleus).
Depending on ______, atoms will have a certain amount of shells.
Depending on their atomic number (number of protons)
For each element, the shell further from the nucleus is called the _______
the valence shell. This shell and its composition will determine most of the element properties.
What will the valence shell determine?
This shell and its composition will determine most of the element properties.
Electrons on the valence shell are known as what?
Electrons on the valence shell are valence electrons.
What can valence electrons do with a sufficient amount of energy?
These electrons, with a sufficient amount of energy, can free themselves from the bond to the nucleus and become free electrons.
What will be the source of the electrical current
The movement of valence electrons freeing themselves from the bond to the nucleus will be the source of electrical current.
Some elements like metals have free what?
free electrons without the need of an external source of energy.
Why are metals good conductors?
some metals have free electrons without the need of an external source of energy
What is the best conductor
The best conductor is silver.
Why is copper the most widely used conductor
Due to the cost of silver, copper is the most widely used.
What other element is a good conductor, apart from metals and silver
Gold is also a good conductor and is used when resistance to corrosion is required.
When is gold used as a conductor
when resistance to corrosion is required.
Semi-conductors have ____ electrons on their valence shell
Semi-conductors have four electrons on their valence shell.
What do semi-conductors require
They require some external source of energy to free electrons.
Why do semi-conductors have 4 electrons on their valence shell
They require some external source of energy to free electrons.
Why can’t insulators carry electrical current
Insulators cannot free electrons and therefore cannot carry electrical current
If an atom loses electrons or gains protons, what happens?
it will have a net positive charge and is called a cation.
If an atom gains electrons or loses protons, what happens?
it will have a net negative charge and is called an anion.
What are isotopes
Atoms of the same element that differ in their numbers of neutrons are called isotopes
