What's the particle that allowed elements to be arranged in the order of their atomic number

protons

Atomic number and protons

After the discovery of protons , scientists realised that the atomic number of an element is the same as the number of protons in its nucleus . In the modern periodic table, the elements are arranged according to their atomic number - not their relative atomic mass .

away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.