atomic structure

whats mass number

number of proton and neutron use mass for massive so bigger more stuff

atomic number is

only number of proton

isotope

has the same number of proton but different number of neutron

What is the typical radius of an atom?

0.1 nm (or 1 x 10^-10 m).

What particle inside the nucleus determines the identity of an element?

Protons.

Who discovered the neutron (evidence for neutral particles in the nucleus)?

James Chadwick.

Why does an atom have an overall electrical charge of zero (neutral)?

Because it has an equal number of positive protons (+1) and negative electrons (-1), which cancel each other out.

Why do elements in the same group have similar chemical properties?

Because they have the same number of electrons in their outer shell.

What type of ions do metals form when they react, and why?

Positive ions (cations)becuase they lose electrons to achieve a stable full outer shell.

What type of ions do non-metals form when they react, and why?

Negative ions (anions), because they gain electrons to achieve a stable full outer shell.

How did John Dalton’s model of the atom describe it in the early 1800s?

solid sphere that cannot be divided

Different elements = different types of solid spheres.

What atomic model did J.J. Thomson propose after discovering the electron

The "plum pudding model" — a ball of positive charge with negative electrons embedded in it.

What experiment disproved the plum pudding model and proved the nucleus exists?

Ernest Rutherford’s alpha particle scattering experiment (firing alpha particles at thin gold foil).

What were the main conclusions of Rutherford's alpha scattering experiment?

that atoms are mostly empty space

The positive charge of the atom is concentrated in a tiny, central region called the nucleus.

suggested nuclear model

How did Niels Bohr adapt the nuclear model of the atom?

He suggested that electrons orbit the nucleus at specific, fixed distances in electron shells (energy levels).

Who provided the experimental evidence that led to the discovery of the neutron?

James Chadwick (about 20 years after the nucleus was accepted).

Why did Mendeleev leave gaps in his early periodic table?

To leave room for undiscovered elements, and he used his table to predict their properties accurately.

What do the group numbers (columns) and period numbers (rows) on the periodic table tell you?

Groups: Number of electrons in the outer shell. Periods: Number of electron shells.

Why do elements in the same group have similar chemical properties?

Because they have the same number of electrons in their outer shell.

Where are metals and non-metals located on the periodic table, and what ions do they form?

Metals: Left/bottom, form positive ions (lose electrons). Non-metals: Right/top, form negative ions (gain electrons).

Why are Group 0 elements (noble gases) unreactive?

Because they have a stable arrangement of electrons with a full outer shell (8 electrons, except Helium which has 2).

How and why does reactivity change as you go down Group 1 (alkali metals)?

Reactivity increases, because the outer electron is further from the nucleus, experiences more shielding, and is lost more easily.

How and why does reactivity change as you go down Group 7 (halogens)?

Reactivity decreases, because the outer shell is further from the nucleus, making it harder to attract and gain an extra electron.

What is a subatomic particle?

a particle that makes up the atom, e.g., proton, neutron, electron

whats a proton?

a subatomic particle with mass of 1 charge of +1

What an electron?

a subatomic particle with mass of 1/2000 and charge of -1

whats a neutron?

a subatomic parcticle with mass 1 and charge 0

What's an atom?

The smallest piece of an element that can exist.

whats was the gold foil experiment

"It was an experiment testing J.J. Thomson's plum pudding model. Positive particles were fired at a thin sheet of gold foil. Thomson thought the positive charge was spread out, so the particles wouldn't be stopped and would go through**.** But instead, most passed through (empty space), some deflected sideways, and a few reflected backward, proving his theory wrong!"

what was the chronological order of the history of the atomic models

1. Dalton (Solid sphere)

2. Thomson (Plum pudding)

3. Rutherford (Nuclear model)

4. Bohr (Shells)

5. Rutherford(Proton) again

6. Chadwick (Neutrons)