M4: Dalton's atomic theory, atom, and isotopes Flashcards
What did John Dalton discovered in 1800s?
He studied the weights of various elements and compounds. He noticed that matter is always combined in fixed ratios based on weight or volume in the case of gases. Chemical compounds always contain the same proportion of elements by mass. Dalton also observed that there could be more than one combination of two elements.
Who is the first scientist who tackles atoms?
democritus
What are the statements in Dalton’s atomic theory?
- All matter is made up of tiny indivisible particles called atom.
- All atoms of a given element are alike but are different from the atoms of any other element.
- A chemical reaction involves a rearrangement of atoms, not a change in atoms themselves.
- Compounds are formed when atoms of different element combine in fixed proportions.
What is atom?
Atoms are the building blocks of matter. They are the smallest particles of an element that still
have the element’s properties. Elements, in turn, are pure substances—such as nickel, hydrogen, and helium—that make up all kinds of matte
What is the relationship of an atom of the same element?
All the atoms of a given element are identical in that they have the same number of protons, one of the building blocks of atoms (see below). They are also different from the atoms of all other elements, as atoms of different elements have different number of protons.
What are subatomic particles and their types?
Subatomic particles make an atom, these are protons, electrons, and neutrons.
What is the difference between protons, electrons, and neutrons?
• protons, which have a positive electric charge.
• electrons, which have a negative electric charge.
• neutrons, which are neutral in electric charge.
What is nucleus?
it is a dense area where all the protons and neutrons are clustered closely.
Where can you find the electrons?
The electrons constantly
move AROUND the nucleus.
What makes an atom neutral?
when there is a balanced amount of proton and electron
What is an atomic number?
The atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. This means that the number of protons is the characteristic which makes each element unique compared to all other elements. Elements are different because of their atomic number.
What is a mass number?
is defined as the total number of protons and neutrons in an atom. It can be calculated by adding the number of neutrons and the number of protons (atomic number) together.
Mass number = atomic number + number of neutrons
How can you illustrate the composition of an atom?
The composition of any atom can be illustrated with a shorthand notation using the atomic
number and the mass number. Both are written before the chemical symbol, with the mass number written as a superscript and the atomic number written as a subscript.
52 CR
24
Another way to refer to a specific atom is to write the mass number of the atom after the name,
separated by a hyphen. The above atom would be written as chromium-52
What is an isotope?
Not all atoms of a given element are identical. Specifically, the number of neutrons can be
variable for many elements. As an example, naturally occurring carbon exists in three forms. Each carbon atom has the same number of protons (6), which is its atomic number. Each carbon atom also contains six electrons in order to maintain electrical neutrality. However, the number of neutrons varies to six, seven, or eight. Isotopes are atoms that have the same atomic number but different mass numbers due to a change in the number of neutrons. These could be Carbon-12, Carbon-13, and Carbon-14
What is the effect of being an isotope? (having different amount of neutron)
While the presence of isotopes affects the mass of an atom, it does not affect its chemical reactivity. Chemical behavior is governed by the number of electrons and the number of protons. Carbon-13 behaves chemically in exactly the same way as the more plentiful carbon-12.
