The woman, who can not be named to protect the identity of the boy, struck him in a "flash of temper" after be broke her phone, Leeds Crown Court was told.
The 37-year-old defendant, from the Wakefield area, initially denied the charge, claiming the boy must have hurt himself, but eventually accepted a charge of assault occasioning actual bodily harm.
Prosecutor Jade Edwards said the alarm was raised by the boy's school when he turned up late one day and staff noticed he was slurring and lethargic.
He then vomited three times in the space of 15 minutes, and confessed that "mummy hit me".
The boy had bruising to his cheek and the back of his head.
He was taken to hospital where he again told nursing staff that his mum had hit him.
He was taken into custody and his mum was arrested.
The court was told he mimicked how his mother hit him, counting out 10 blows to his head, and was left feeling "sad" because his head was hurting.
He suffered bruising to his cheek, to the back of his head and a scratch behind his ear.
He is currently in foster care.
She later admitted she had hit him after he covered the bathroom in toothpaste.
No mitigation was offered after Judge Graham Reeds QC said he would not be sending the woman to jail as he accepted it had been a one-off incident.
He said: "What you did was out of character and a flash of temper. You have now admitted what you did even though at the magistrates' court you gave a not guilty plea.
"Your son has been taken into custody and it will take a while for relations to be built, if they can be. Whether that chance is realistic is up to the family court, not me."
She was given a 12-month community order and 30 rehabilitation activity requirement days.